Calcium Channel Blocker Overdose

Topic Overview

Summary

Calcium channel blocker (CCB) overdose is a potentially lethal cardiovascular poisoning characterized by profound bradycardia, hypotension, cardiogenic shock, and metabolic derangements including hyperglycaemia. Non-dihydropyridines (verapamil, diltiazem) predominantly cause cardiac depression with bradycardia and conduction abnormalities, while dihydropyridines (amlodipine, nifedipine) primarily produce peripheral vasodilation. However, in overdose, all CCBs lose selectivity and can cause both cardiac and vascular toxicity. [1,2]

Management requires rapid recognition and aggressive multimodal therapy. First-line treatments include intravenous calcium salts (calcium chloride or gluconate), high-dose insulin euglycaemic therapy (HIET), and vasopressor/inotropic support. [3,4] HIET has emerged as the most effective antidote, with bolus insulin 1 unit/kg followed by infusions of 0.5-10 units/kg/hr, alongside dextrose to maintain euglycaemia. [5] Refractory cases may require intravenous lipid emulsion (ILE) for lipophilic CCBs and venoarterial extracorporeal membrane oxygenation (VA-ECMO) as rescue therapy. [3,6]

Amlodipine has become the most common CCB involved in overdose, accounting for approximately 62% of cases in recent series. [7] Dihydropyridine overdoses present unique challenges due to profound vasoplegia requiring vasopressor-predominant therapy, whereas non-dihydropyridines typically require inotropic support. Mortality ranges from 3-10% with appropriate treatment but can exceed 50% in untreated severe poisoning. [7,8]

Key Facts

• Mechanism: L-type calcium channel blockade → ↓cardiac contractility, ↓conduction, ↓AV nodal function, peripheral vasodilation
• Classical triad: Bradycardia, hypotension, hyperglycaemia (diagnostic clue)
• Non-dihydropyridines (verapamil, diltiazem): Cardiac-selective — bradycardia, AV block, negative inotropy
• Dihydropyridines (amlodipine, nifedipine): Vascular-selective — vasodilation, reflex tachycardia (may mask toxicity initially)
• First-line therapy: IV calcium + HIET + vasopressors/inotropes [3,4]
• Most effective antidote: High-dose insulin (1 unit/kg bolus, then 0.5-10 units/kg/hr infusion) [5,9]
• Amlodipine: Long half-life (30-50 hours), delayed toxicity, prolonged symptoms
• Sustained-release formulations: Delayed peak toxicity (6-24 hours), prolonged course

Clinical Pearls

Hyperglycaemia as a diagnostic clue: CCBs block pancreatic β-cell calcium channels → ↓insulin secretion → hyperglycaemia. Glucose > 11 mmol/L in a hypotensive patient without known diabetes suggests CCB overdose.

HIET is the definitive antidote: High-dose insulin improves myocardial contractility independent of calcium channels through enhanced glucose uptake and utilization by cardiomyocytes. Start early — don't wait for severe shock. [5,9]

Calcium chloride vs gluconate: Calcium chloride delivers 3× more elemental calcium per mole (13.6 mEq/10 mL vs 4.7 mEq/10 mL). Use chloride via central line for severe toxicity; gluconate is safer peripherally. [10]

Amlodipine paradox: Despite causing vasodilation, HIET may worsen hypotension in pure dihydropyridine overdose due to additional vasodilatory effects. Prioritize vasopressors (noradrenaline) over inotropes. [7,11]

Sustained-release trap: Symptoms may be minimal initially but deteriorate dramatically 6-24 hours post-ingestion. Observe all sustained-release CCB ingestions for ≥24 hours. [1,12]

Don't rely on atropine or pacing alone: CCB-induced bradycardia is mediated by direct AV nodal depression, not vagal tone. Atropine is often ineffective; transcutaneous pacing may capture but not improve cardiac output. [1,13]

Why This Matters Clinically

CCB overdose represents one of the most challenging toxicological emergencies because:

1. Refractory to conventional resuscitation: Standard Advanced Cardiac Life Support (ACLS) measures often fail
2. Rapidly progressive: Can deteriorate from mild hypotension to cardiac arrest within hours
3. High mortality: Untreated severe CCB toxicity has > 50% mortality; appropriate HIET reduces this to 3-10% [7,8]
4. Delayed presentation: Sustained-release formulations and amlodipine's long half-life create a "therapeutic window" where aggressive early treatment prevents deterioration
5. Requires specialized knowledge: HIET dosing, lipid emulsion therapy, and ECMO are not routine ACLS interventions

---

Visual Summary

Visual assets to be added:

• CCB classification and mechanism of action diagram
• Dihydropyridine vs non-dihydropyridine comparison table with clinical effects
• CCB overdose management algorithm (mild/moderate/severe pathways)
• HIET dosing protocol with monitoring requirements
• Calcium therapy dosing (chloride vs gluconate equivalence)
• Timeline of toxicity for immediate vs sustained-release formulations

---

Epidemiology

Incidence \u0026 Trends

• CCBs account for approximately 40% of cardiovascular drug exposures but > 65% of cardiovascular medication-related deaths [1,14]
• Increasing incidence: Dihydropyridine overdoses have risen significantly — median 9 cases/year (2014-2023) vs 3 cases/year (2004-2013), a 3-fold increase [7]
• Amlodipine: Now the most common CCB in overdose (62% of cases), reflecting its widespread prescription for hypertension [7]
• Intentional overdose: 70-80% of severe cases are deliberate self-poisoning in adults
• Accidental overdose: More common in elderly (therapeutic error, renal impairment) and children (exploratory ingestion)

Mortality

• Overall mortality: 3-10% with appropriate treatment [7,8]
• Severe poisoning (untreated): Mortality > 50% [8]
• Verapamil: Historically highest mortality among CCBs (due to potent cardiac depression)
• Diltiazem: ICU admission rate 52%; high-dose insulin required in 67% of severe cases [7]
• Amlodipine: Despite lower per-tablet toxicity, accounts for most deaths due to high prevalence

Risk Factors for Severe Toxicity

• Sustained-release formulations: Delayed, prolonged toxicity
• Co-ingestion with β-blockers: Synergistic cardiac depression
• Pre-existing cardiac disease: Heart failure, conduction abnormalities, ischaemic heart disease
• Renal impairment: Reduced clearance (especially diltiazem, verapamil)
• Elderly age: Reduced physiological reserve, polypharmacy

Common CCB Agents

*In overdose, dihydropyridines can also cause bradycardia and myocardial depression due to loss of selectivity

---

Pathophysiology

Molecular Mechanism

L-type Calcium Channel Blockade [1,2,25]

1. CCBs bind to L-type voltage-gated calcium channels on cardiac myocytes, vascular smooth muscle, and pancreatic β-cells
2. Blockade prevents calcium influx during cellular depolarization
3. ↓Intracellular calcium → impaired excitation-contraction coupling

Cardiac Effects

• Sinoatrial (SA) node: ↓Automaticity → bradycardia
• Atrioventricular (AV) node: ↓Conduction velocity → prolonged PR interval, AV block (1°, 2°, 3°)
• Ventricular myocardium: ↓Contractility → negative inotropy → ↓cardiac output → cardiogenic shock
• Loss of selectivity in overdose: Even "vascular-selective" dihydropyridines cause cardiac depression at toxic doses [1,7]

Vascular Effects

• Arterial smooth muscle: ↓Contractility → peripheral vasodilation → ↓systemic vascular resistance (SVR) → distributive shock
• Dihydropyridines: Predominant vasodilation → reflex tachycardia (may initially mask toxicity) → eventual cardiac depression
• Combined shock: Severe CCB toxicity produces both cardiogenic shock (↓contractility) and distributive shock (↓SVR)

Metabolic Effects [2,27]

• Pancreatic β-cells: Calcium required for insulin vesicle exocytosis; CCBs block this → ↓insulin secretion → hyperglycaemia (pathognomonic sign)
• Peripheral tissues: ↓Insulin-mediated glucose uptake → worsens hyperglycaemia
• Metabolic acidosis: Tissue hypoperfusion (shock) → lactate accumulation

Why High-Dose Insulin Euglycaemic Therapy (HIET) Works

Mechanisms of Benefit [5,9,16,27]

1. Positive inotropy (calcium-independent):

   • Insulin has direct positive inotropic effects on myocardium
   • Increases myocyte calcium sensitivity to available intracellular calcium
   • Enhances contractility despite L-type channel blockade

2. Metabolic support:

   • Cardiomyocytes in CCB toxicity shift from fatty acid to carbohydrate metabolism
   • Insulin promotes glucose uptake into myocytes (via GLUT-4 translocation)
   • Enhances glycolysis → ATP production → improved contractility

3. Vasodilation (peripheral):

   • Insulin causes peripheral vasodilation (via nitric oxide)
   • Beneficial in non-dihydropyridine overdose (↓afterload)
   • Problematic in dihydropyridine overdose → may worsen hypotension → requires concurrent vasopressors [11]

Animal Studies: High-dose insulin superior to calcium, glucagon, adrenaline, and vasopressin for survival in CCB-poisoned animals [5,9]

Why Hyperglycaemia Occurs

• Calcium-dependent insulin secretion: Glucose → β-cell depolarization → voltage-gated Ca²⁺ channels open → Ca²⁺ influx → insulin vesicle exocytosis
• CCBs block this pathway → insulin secretion impaired despite elevated glucose → hyperglycaemia
• Diagnostic clue: Glucose > 11 mmol/L in hypotensive patient without diabetes = consider CCB overdose
• Paradox: Give high-dose insulin despite hyperglycaemia (insulin acts as inotrope, not glucose control)

---

Clinical Presentation

Cardiovascular Manifestations

Non-Dihydropyridines (Verapamil, Diltiazem)

• Bradycardia: HR typically 30-50 bpm (can be profound less than 30 bpm)
• AV conduction abnormalities: 1st-degree block (prolonged PR), 2nd-degree (Mobitz I or II), 3rd-degree (complete heart block), junctional escape rhythms
• Hypotension: Multifactorial — ↓cardiac output (bradycardia + negative inotropy), some vasodilation
• Cardiogenic shock: ↓Contractility → pulmonary oedema, ↓end-organ perfusion
• Cardiac arrest: Asystole, pulseless electrical activity (PEA)

Dihydropyridines (Amlodipine, Nifedipine)

• Initial reflex tachycardia: Baroreceptor response to vasodilation (early phase)
• Later bradycardia: As toxicity worsens, direct cardiac effects overcome reflex → bradycardia
• Profound hypotension: Predominantly vasodilatory → "warm shock" initially → later "cold shock"
• Flushing: Peripheral vasodilation → warm, flushed peripheries (early)
• Dysrhythmias: Junctional rhythms, occasional AV block (less common than non-dihydropyridines) [7]

Metabolic Manifestations

• Hyperglycaemia: Glucose often 15-30 mmol/L (can be > 40 mmol/L) [1,2]
  • "Timing: Develops within 2-6 hours of significant overdose"
  • "Diagnostic value: High sensitivity for CCB overdose in appropriate clinical context"
• Metabolic acidosis: Lactic acidosis from tissue hypoperfusion (late, severe cases)
• Hypokalaemia: May occur with HIET (insulin drives K⁺ intracellularly) — monitor and replace

Neurological Manifestations

• Altered consciousness: Confusion, drowsiness, lethargy (due to cerebral hypoperfusion)
• Coma: GCS less than 8 in severe poisoning
• Seizures: Rare; more common with severe cerebral hypoperfusion or verapamil specifically
• Stroke: Rare complication of profound, prolonged hypotension

Gastrointestinal Manifestations

• Nausea and vomiting: Common, especially early
• Bowel ischaemia: Rare; occurs with prolonged shock → mesenteric hypoperfusion

Timeline of Toxicity

Immediate-Release Formulations

• Onset: 30 minutes to 2 hours post-ingestion
• Peak toxicity: 2-6 hours
• Duration: 6-24 hours (verapamil, diltiazem); up to 72 hours (amlodipine)

Sustained-Release Formulations [1,12]

• Onset: Often delayed 6-12 hours (can be asymptomatic initially)
• Peak toxicity: 12-24 hours (beware late deterioration)
• Duration: 24-72 hours (can persist > 5 days with amlodipine SR)
• Clinical trap: Patient may appear well initially, then deteriorate dramatically

Amlodipine (long half-life: 30-50 hours)

• Delayed onset: Often 6-12 hours
• Prolonged toxicity: Symptoms can persist 3-5 days
• Rebound: Patients may appear to improve then re-deteriorate

Red Flags Indicating Severe Toxicity

---

Clinical Examination

General Inspection

• Conscious level: Alert → drowsy → confused → comatose (progressive with worsening shock)
• Distress: Dyspnoea (pulmonary oedema), pallor, cold/warm peripheries

Vital Signs

• Heart rate: Bradycardia (non-DHP); may be tachycardic initially (DHP); junctional rhythms
• Blood pressure: Hypotension (SBP often 60-90 mmHg in severe cases)
• Respiratory rate: Often normal or increased (compensatory, or pulmonary oedema)
• Oxygen saturation: May be reduced if pulmonary oedema
• Temperature: Usually normal (contrast with beta-blocker overdose where hypothermia more common)

Cardiovascular Examination

• Pulse: Weak, thready, bradycardic (or irregular if AV block)
• Jugular venous pressure (JVP): May be elevated (cardiogenic shock, AV dissociation)
• Heart sounds: Bradycardia, irregular rhythm (AV block), ±murmurs if pre-existing
• Peripheral perfusion:
  • Warm peripheries (early dihydropyridine — vasodilation)
  • Cold, clammy peripheries (late, all CCBs — cardiogenic shock)

Respiratory Examination

• Crackles (bibasal): Pulmonary oedema (cardiogenic shock)
• Respiratory distress: Tachypnoea, use of accessory muscles

Neurological Examination

• GCS: Assess for altered consciousness (cerebral hypoperfusion)
• Pupils: Usually normal (no direct pupillary effect; contrast with opioids)
• Focal neurology: Rare (stroke if prolonged hypotension)

Skin

• Flushed, warm: Dihydropyridine-induced vasodilation (early)
• Pale, cool, clammy: Severe shock (late, all CCBs)

---

Investigations

Bedside Tests

ECG (12-lead and continuous monitoring)

Point-of-Care Glucose

• Immediate bedside glucose: Essential initial test
• Hyperglycaemia (> 11 mmol/L): Strongly suggestive of CCB overdose in appropriate context
• Serial monitoring: Hourly if HIET commenced (target 8-12 mmol/L during HIET)

Blood Tests

Initial Panel

Additional Tests

CCB Drug Levels

• Not routinely available or clinically useful in acute management
• Not recommended: Do not delay treatment waiting for levels
• Manage clinically: Base treatment on clinical signs, not drug levels

Imaging

Chest X-Ray

• Indications: Hypoxia, respiratory distress, suspected pulmonary oedema
• Findings: Pulmonary oedema (bilateral infiltrates), cardiomegaly (if pre-existing), normal in many cases

Echocardiography (Transthoracic or Transoesophageal)

• Indications: Cardiogenic shock, refractory hypotension, unclear aetiology
• Findings: ↓Left ventricular ejection fraction (LVEF), ↓global contractility, ±valvular abnormalities (pre-existing)
• Utility: Guides therapy (inotropes vs vasopressors); assesses ECMO candidacy

CT Brain

• Indications: Focal neurology, prolonged GCS ↓, concern for stroke
• Findings: Usually normal; rarely ischaemic stroke (prolonged hypotension)

Toxicological Screening

• Urine drug screen: Consider if polypharmacy suspected
• Paracetamol / salicylate: Co-ingestion common in deliberate self-poisoning
• Beta-blocker screen: CCB + β-blocker co-ingestion = synergistic cardiac toxicity

---

Differential Diagnosis

Cardiovascular Causes of Bradycardia + Hypotension

Toxicological Causes

---

Management

Initial Resuscitation (A-E Approach)

Airway

• Assess: GCS less than 8 → consider intubation (protect airway, ventilatory support)
• Secure: Endotracheal intubation if impaired consciousness or respiratory failure

Breathing

• High-flow oxygen: Target SpO₂ > 94%
• Assess: Respiratory rate, work of breathing, bilateral air entry, crackles (pulmonary oedema)
• Mechanical ventilation: If respiratory failure or for airway protection

Circulation

• IV access: Two large-bore cannulae (16G or larger) ±central line (for calcium chloride, vasopressors)
• Fluid resuscitation:
  • "Bolus: 500 mL-1 L crystalloid (0.9% NaCl) initially"
  • "Caution: Limited benefit if cardiogenic shock predominates; avoid fluid overload → pulmonary oedema"
  • "Reassess: After each bolus (BP, JVP, lung fields)"
• Continuous monitoring: ECG (telemetry), SpO₂, invasive arterial BP (if severe), ±central venous pressure

Disability

• GCS: Assess and monitor (cerebral perfusion = MAP - ICP ≈ MAP in most cases)
• Glucose: Bedside glucose immediately (diagnose hyperglycaemia)

Exposure

• Temperature: Monitor (usually normal in CCB overdose)
• Skin: Assess perfusion (warm vs cold peripheries)

Decontamination (if within appropriate time window)

Do NOT induce vomiting (risk aspiration, ineffective)

---

Specific Antidotal Therapy

1. Intravenous Calcium — First-Line, Immediate Treatment [3,10,20]

Mechanism: Increases extracellular calcium concentration → overcomes competitive calcium channel blockade → improves inotropy and vascular tone (limited efficacy, but rapid and safe)

Calcium Chloride vs Calcium Gluconate — Comprehensive Comparison

Pharmacological Differences

Dosing Protocols

Calcium Chloride Protocol (Preferred for Severe CCB Toxicity) [10,20]

Calcium Gluconate Protocol (Safe for Peripheral Access) [10]

Equivalence Conversions

Elemental Calcium Equivalents:

• 10 mL calcium chloride 10% = 30 mL calcium gluconate 10% (to deliver same elemental calcium)
• 1 g calcium chloride = 3 g calcium gluconate (approximate equivalent)

Example: To deliver 13.6 mEq elemental calcium:

• Give 10 mL calcium chloride 10%, OR
• Give 30 mL calcium gluconate 10%

Clinical Decision-Making: Which Calcium Salt?

Use Calcium Chloride When:

• Severe CCB toxicity (SBP less than 70 mmHg, cardiac arrest, refractory shock)
• Central line in place (can administer safely)
• Need rapid calcium delivery (immediate ionization, no hepatic metabolism required)
• Hepatic impairment (gluconate requires liver to convert to ionized calcium)
• Resuscitation setting (higher calcium concentration = less volume)

Use Calcium Gluconate When:

• Peripheral IV access only (safer, less vein irritation)
• Mild-moderate toxicity (SBP 70-90 mmHg, stable patient)
• Extravasation risk (agitated patient, difficult IV access)
• Prolonged infusions (continuous therapy over 24-48 hours)
• Normal hepatic function (adequate metabolism to ionized calcium)

Expected Haemodynamic Response [10,20]

Timing of Effect:

• Onset: 1-5 minutes after bolus
• Peak effect: 5-10 minutes
• Duration: 10-30 minutes (transient)

Magnitude of Response (evidence from case series) [10]:

• Systolic BP increase: 5-15 mmHg (average 10 mmHg)
• Heart rate increase: 5-10 bpm (inconsistent)
• Success rate: 30-50% show modest improvement
• Limitation: Rarely sufficient as monotherapy; use as bridge to HIET

Why Limited Efficacy? [10]

• CCBs bind with high affinity to L-type channels (competitive inhibition difficult to overcome)
• Massive overdose saturates channels (extracellular calcium cannot compete effectively)
• Calcium does not address metabolic derangements (hyperglycaemia, insulin deficiency)

Monitoring During Calcium Therapy

Laboratory Monitoring:

Clinical Monitoring:

• IV site inspection (every hour if peripheral gluconate; extravasation risk)
• Continuous BP, HR (assess haemodynamic response)
• Signs of hypercalcaemia: Confusion, weakness, polyuria (rare in acute setting)

Adverse Effects and Management

1. Bradycardia (if administered too rapidly)

• Mechanism: Calcium → ↑vagal tone → AV node suppression
• Prevention: Infuse over 5-10 minutes (not IV push)
• Management: Stop infusion; usually self-limiting within 5 minutes

2. Tissue Necrosis (extravasation of calcium chloride) [20]

• Mechanism: Hyperosmolar solution → direct tissue damage → necrosis
• Prevention: Always use central line for calcium chloride
• Management: Stop infusion immediately; hyaluronidase infiltration (1500 units SC around site); surgical debridement if necrosis develops

3. Hypercalcaemia (prolonged high-dose infusions)

• Risk factors: Continuous infusions > 24 hours, renal impairment
• Symptoms: Confusion, muscle weakness, polyuria, shortened QT interval
• Management: Stop calcium infusions; IV fluids; furosemide (if symptomatic); rarely requires haemodialysis

4. Hypophosphataemia (secondary to hypercalcaemia)

• Mechanism: Calcium-phosphate reciprocal relationship
• Management: Monitor phosphate daily; replace if less than 0.5 mmol/L

Key Clinical Pearls

Calcium is a temporizing measure, not definitive therapy: Provides modest, transient haemodynamic improvement (5-10 mmHg BP increase for 10-20 minutes). Use as bridge to HIET, which is the definitive antidote. [10]

Calcium chloride is 3× more potent: For severe toxicity with central access, calcium chloride delivers more calcium in less volume (critical in shock states). [20]

Never give calcium chloride peripherally: Extravasation causes tissue necrosis requiring surgical debridement. Use gluconate if only peripheral access. [20]

Check ionized calcium, not total calcium: Total calcium includes protein-bound calcium (not physiologically active). Ionized calcium reflects bioavailable calcium. [10]

Magnesium matters: Hypomagnesaemia reduces calcium efficacy. Check Mg²⁺ if patient not responding to calcium therapy; replace if less than 0.7 mmol/L. [10]

---

2. High-Dose Insulin Euglycaemic Therapy (HIET) — Most Effective Antidote [3,4,5,9]

Mechanism: Positive inotropy (calcium-independent), enhanced myocardial glucose uptake and ATP production, peripheral vasodilation

Indications

• All moderate to severe CCB overdose with hypotension and/or bradycardia
• Start early: Do not wait for shock; initiate when hypotension develops (SBP less than 90 mmHg)
• First-line therapy alongside calcium and vasopressors [3,4]

HIET Initiation Protocol

Target Glucose During HIET: 8-12 mmol/L (avoid hypoglycaemia less than 4 mmol/L and excessive hyperglycaemia > 15 mmol/L)

HIET Titration Algorithm

Based on haemodynamic response [5,9,15,19]:

HIET Dextrose Management Protocol

Dextrose concentration and infusion rate:

Typical dextrose requirements:

• Initial: 200-500 mL/hr of 10% dextrose
• High-dose HIET (> 5 units/kg/hr): May require 500-1000 mL/hr of 20% dextrose
• Fluid overload risk: Consider central line for higher concentrations (50% dextrose) to reduce volume

HIET Potassium Management Protocol

Insulin-induced hypokalaemia is predictable and must be anticipated [9,19]:

Key principles:

• Pre-emptive replacement: Start KCl infusion (10-20 mEq/hr) when initiating HIET, even if K⁺ normal
• Central line preferred: For high-dose KCl infusions (> 20 mEq/hr) to avoid peripheral vein irritation
• Continuous ECG monitoring: Watch for signs of hypokalaemia (U waves, flattened T waves, QT prolongation, arrhythmias)

Efficacy

• Response time: Improvement in BP/HR often within 15-60 minutes [5,9]
• Success rate: 80-100% in case series [5,9,15]
• Superior to alternatives: Animal studies show HIET better than calcium, glucagon, adrenaline [5]
• Mortality reduction: Early HIET associated with reduced ICU length of stay and mortality [15]

Monitoring During HIET

• Glucose: Hourly (initially), then every 2 hours once stable; every 30 min if titrating
• Potassium: Every 2-4 hours; hourly if less than 3.5 mmol/L
• BP, HR: Continuous invasive arterial monitoring (preferred for accurate titration)
• Lactate: Every 4-6 hours (marker of tissue perfusion and shock severity)
• Fluid balance: Dextrose infusions deliver significant volume → monitor JVP, lung fields, urine output
• Signs of fluid overload: Consider furosemide if pulmonary oedema develops

Adverse Effects

• Hypoglycaemia (20-40% of cases): Most common; prevent with dextrose co-infusion and frequent monitoring [9,19]
• Hypokalaemia (30-50% of cases): Insulin drives K⁺ intracellularly; replace aggressively (aim K⁺ 4.0-5.0 mmol/L) [9]
• Fluid overload (10-20% of cases): High-volume dextrose infusions → pulmonary oedema (especially if cardiogenic shock); manage with furosemide or haemofiltration
• Vasodilation (in dihydropyridine overdose): Insulin's peripheral vasodilatory effect may worsen hypotension in pure amlodipine overdose → mitigate with vasopressors [11]
• Hypomagnesaemia: May occur with prolonged HIET; check Mg²⁺ if K⁺ refractory despite replacement

Weaning HIET

• Once haemodynamically stable for 12-24 hours (SBP > 100 mmHg off vasopressors), reduce insulin by 50% every 6-12 hours
• Continue glucose monitoring for 24 hours after stopping insulin (rebound hypoglycaemia risk)
• Gradual weaning: Abrupt cessation may cause haemodynamic deterioration; taper slowly
• Extended HIET: Amlodipine may require 48-72 hours of HIET due to long half-life [7]

HIET Mechanism of Action — Detailed

1. Positive Inotropic Effects (Calcium-Independent) [5,9]

• Insulin increases myocardial contractility independent of L-type calcium channels
• Enhances myocyte calcium sensitivity to available intracellular calcium
• Activates phosphatidylinositol 3-kinase (PI3K) pathway → ↑contractile protein sensitivity

2. Metabolic Rescue of Cardiomyocytes [5,16]

• Substrate shift: CCB toxicity impairs fatty acid metabolism in cardiomyocytes
• Insulin promotes glucose uptake: Via GLUT-4 translocation to cell membrane
• Enhanced glycolysis: ↑ATP production → improved contractility
• Reversal of metabolic acidosis: Improved cellular energetics reduce lactate production

3. Peripheral Vasodilation [9]

• Insulin stimulates nitric oxide (NO) production in endothelium → vasodilation
• Beneficial: In non-dihydropyridine overdose (↓afterload improves cardiac output)
• Problematic: In dihydropyridine overdose (worsens vasodilatory shock) → requires concurrent vasopressor therapy

4. Anti-Inflammatory and Cardioprotective Effects

• Reduces myocardial inflammation and oxidative stress
• May reduce reperfusion injury in prolonged shock states

---

3. Vasopressor and Inotropic Support [1,3,13]

Indications: Hypotension despite IV fluids and calcium

Choice of Agent (depends on type of CCB and shock mechanism)

Strategy by CCB Type

• Amlodipine (dihydropyridine): Noradrenaline (vasopressor) first-line; add adrenaline if refractory; use HIET cautiously (may worsen vasodilation) [7,11]
• Verapamil / Diltiazem (non-dihydropyridine): Adrenaline (inotropy + chronotropy) or dobutamine + noradrenaline; HIET very effective [1,3]

High Doses Often Required: CCB overdose frequently requires vasopressor/inotrope doses exceeding typical ranges [7,13]

---

4. Other Adjunct Treatments

Atropine (Limited Efficacy)

• Dose: 0.6-1.2 mg IV (repeat every 3-5 min; max 3 mg)
• Mechanism: Blocks vagal tone → ↑HR
• Efficacy: Poor in CCB overdose (bradycardia is from direct SA/AV nodal depression, not vagal tone) [1,13]
• Use: May try for symptomatic bradycardia but do not rely on it

Glucagon (Minimal Benefit for CCBs) [1,13,21]

• Dose: 5-10 mg IV bolus (over 1-2 minutes), then 2-10 mg/hr infusion
• Mechanism:
  • Bypasses β-adrenergic receptors → binds to glucagon receptors on cardiac myocytes
  • Activates adenylyl cyclase → ↑cAMP → ↑intracellular calcium (independent of L-type channels)
  • Positive inotropic and chronotropic effects (increases contractility and heart rate)
  • Glycogenolysis in liver → ↑blood glucose (may worsen CCB-induced hyperglycaemia)
• Pharmacokinetics:
  • "Onset: 1-3 minutes"
  • "Peak effect: 5-10 minutes"
  • "Duration: 10-15 minutes (short-lived)"
  • Hepatic metabolism; renal clearance
• Efficacy:
  • Effective for β-blocker overdose (bypasses blocked β-receptors) [21]
  • Minimal benefit in CCB overdose (does not overcome L-type channel blockade effectively) [1,13]
  • "Animal studies: Inferior to HIET for CCB toxicity [21]"
  • "Human case reports: Variable, often disappointing response in pure CCB overdose [1,13]"
• Clinical Use:
  • Not routinely recommended for pure CCB overdose [3,13]
  • May try if diagnostic uncertainty (CCB vs β-blocker vs mixed overdose)
  • Can be useful in mixed CCB + β-blocker overdose (synergistic toxicity)
• Adverse Effects:
  • Nausea and vomiting (very common, 50-80% of patients) → aspiration risk
  • Hyperglycaemia (worsens CCB-induced hyperglycaemia; less concerning as transient)
  • Hypokalaemia (β₂-mediated; similar to insulin)
  • Anaphylaxis (rare; glucagon is porcine or recombinant protein)
  • Ileus (with prolonged high-dose infusions)
• Preparation:
  • Glucagon supplied as powder (1 mg vials); reconstitute with diluent
  • High-dose therapy (5-10 mg) requires multiple vials
  • Compatible with 0.9% NaCl or 5% dextrose for infusions
• Why Limited Efficacy in CCB Overdose?:
  • Glucagon increases intracellular cAMP → calcium influx via L-type channels
  • But CCBs block L-type channels → glucagon-induced calcium influx still blocked
  • This mechanism works for β-blockers (different receptor, same downstream calcium channel)
  • For CCBs, HIET superior (calcium-independent mechanism) [5,21]
• Evidence Summary [1,13,21]:
  • "Animal studies: Glucagon modestly improves BP in CCB-poisoned animals, but inferior to insulin"
  • "Human case reports: Inconsistent benefit; often no haemodynamic improvement"
  • "Guideline recommendation: Class 2C (weak recommendation, low-quality evidence) — consider only if no other options [3]"

Key Clinical Pearl:

Glucagon is for β-blockers, not CCBs: If patient overdosed on β-blocker, glucagon is first-line (bypasses blocked receptors). If CCB overdose, glucagon has minimal benefit because it still requires L-type calcium channels (which are blocked). Use HIET instead. [1,13,21]

Mixed overdose exception: In CCB + β-blocker co-ingestion (synergistic toxicity), glucagon may help reverse the β-blocker component while HIET addresses CCB toxicity. Consider combination therapy. [21]

Cardiac Pacing (Temporizing, Not Definitive) [1,13,22]

Indications for Pacing in CCB Overdose

Reasonable to Consider:

• Severe symptomatic bradycardia (HR less than 40 bpm with hypotension, altered consciousness, or shock)
• High-grade AV block (Mobitz II, 3rd-degree complete heart block with slow ventricular escape)
• Asystole or impending cardiac arrest (as part of ACLS resuscitation)
• Bridge to definitive therapy (temporizing while HIET takes effect, or awaiting ECMO)

Timing:

• Initiate pacing early if severe bradycardia unresponsive to atropine and calcium
• Do not delay HIET or vasopressors while attempting pacing
• Consider pacing concurrently with HIET (not as replacement for medical therapy)

Pacing Modalities

1. Transcutaneous Pacing (TCP) [13,22]

Advantages:

• Non-invasive: Rapid to apply (1-2 minutes)
• Immediate availability: No procedural skills required
• Bridge to transvenous pacing: Stabilizes patient for procedure

Technique:

• Electrode placement: Anterior-posterior (AP) or anterior-lateral (AL) position
  • "AP: Anterior pad left parasternal (4th-5th intercostal space); posterior pad between scapulae"
  • "AL: Anterior pad left mid-axillary line (5th intercostal space); lateral pad right infraclavicular"
• Pacing mode: Demand pacing (synchronizes with intrinsic rhythm)
• Rate: 60-80 bpm (physiological range)
• Output: Start at 0 mA; increase gradually until electrical capture (typically 50-100 mA)
• Capture confirmation: Palpate pulse with each paced beat; confirm BP improvement

Limitations:

• Painful: Requires sedation/analgesia (e.g., fentanyl 50-100 mcg IV, midazolam 2-5 mg IV)
• Capture without mechanical output: Electrical capture on ECG does not guarantee cardiac output improvement [13,22]
• Myocardial stunning: Underlying myocardial depression (negative inotropy from CCB) persists despite pacing
• Failure to improve BP: Even with 1:1 capture, stroke volume may remain low → no haemodynamic benefit

2. Transvenous Pacing (TVP) [13]

Advantages:

• More reliable capture: Direct endocardial stimulation
• Better tolerated: Less painful than TCP (no chest wall muscle stimulation)
• Sustained pacing: Can be maintained for days if needed

Technique:

• Venous access: Internal jugular (IJ) or subclavian vein (preferred); femoral vein (alternative)
• Pacing catheter: Balloon-tipped temporary pacing wire (e.g., 5-6 Fr)
• Fluoroscopy or echo-guided placement: Position lead in right ventricular (RV) apex
• Pacing parameters:
  • "Mode: VVI (ventricular demand pacing)"
  • "Rate: 60-80 bpm"
  • "Output: 2-5 mA (threshold testing); set output 2-3× capture threshold"
  • "Sensitivity: Adjust to sense intrinsic QRS complexes"

Limitations:

• Time-consuming: Requires procedural skills, sterile technique (10-30 minutes to insert)
• Procedural risks: Pneumothorax, haemothorax, arterial puncture, arrhythmias (catheter-induced VT/VF)
• Same fundamental problem: Does not address negative inotropy or vasodilation [13]
• Lead displacement: Risk of dislodgement (especially in agitated patient)

Why Pacing Often Fails in CCB Overdose [1,13,22]

Fundamental Pathophysiology:

Clinical Reality [13,22]:

• Pacing may achieve electrical capture (QRS complex after each pacing spike on ECG)
• But mechanical capture (palpable pulse, improved CO) often fails to occur
• Even with mechanical capture, stroke volume remains low (due to ↓contractility)
• Blood pressure improvement minimal or absent (5-10 mmHg at best; often no change)

Evidence [1,13]:

• Case reports: Pacing frequently unsuccessful at improving haemodynamics in CCB overdose
• Pacing may "buy time" (prevent asystole) but does not reverse toxicity
• HIET and vasopressors more effective at improving cardiac output and BP

Optimal Use of Pacing in CCB Overdose

Pacing is a BRIDGE, not a SOLUTION [1,13,22]:

✓ Appropriate Use:

• Temporizing measure while waiting for HIET to take effect (15-60 minutes to work)
• Bridge to ECMO (maintain minimal perfusion during cannulation)
• Prevent asystole (in profound bradycardia with impending arrest)
• Part of multi-modal therapy (pacing + HIET + vasopressors + calcium)

✗ Inappropriate Expectations:

• Do NOT expect pacing alone to reverse shock
• Do NOT delay HIET or vasopressors to attempt pacing
• Do NOT rely on pacing as primary therapy

Clinical Decision Algorithm [3,13]:

Severe bradycardia (HR less than 40 bpm) + hypotension in CCB overdose
↓
1. Give calcium (immediate)
2. Start HIET (within 5-10 minutes)
3. Start vasopressors/inotropes (concurrent)
4. Try atropine (1.2 mg IV) — often ineffective but rapid/safe
↓
STILL bradycardic and deteriorating?
↓
5. Initiate transcutaneous pacing (TCP)
   - Sedate patient (fentanyl + midazolam)
   - Capture at lowest effective output
   - Assess haemodynamic response (BP, perfusion)
↓
No improvement despite pacing?
↓
6. Escalate HIET dose (increase insulin to 2-5 units/kg/hr)
7. Increase vasopressor dose
8. Contact ECMO centre (arrange transfer if refractory)
↓
Consider transvenous pacing ONLY if:
- TCP failed to capture
- Prolonged therapy anticipated (> 24 hours)
- Patient stable enough for procedure

Evidence Summary [1,13,22]

Animal Studies:

• Pacing improves heart rate but not cardiac output in CCB-poisoned animals
• Combination of pacing + HIET superior to pacing alone

Human Case Reports:

• Variable success; many reports of pacing failure despite electrical capture
• Patients who improve often had concurrent HIET, vasopressors, calcium (cannot isolate pacing effect)

Guidelines [3]:

• AHA 2023: Pacing may be considered (Class 2B, Level C — weak recommendation, expert opinion)
• Recognized as temporizing measure, not definitive therapy
• Should not delay or replace HIET, vasopressors, calcium

Key Clinical Pearls:

Electrical capture ≠ haemodynamic improvement: ECG may show perfect 1:1 pacing, but patient remains hypotensive because underlying myocardial depression and vasodilation persist. Always assess pulse and BP, not just ECG. [13,22]

Pacing buys time, HIET saves lives: Use pacing to prevent asystole and maintain minimal perfusion while HIET (the definitive antidote) takes effect. Never delay HIET to attempt pacing. [1,3]

If pacing fails, escalate to ECMO: Refractory bradycardia + hypotension despite pacing + HIET + vasopressors = indication for VA-ECMO. Early ECMO consultation critical (within 2-4 hours). [3,17]

---

5. Rescue Therapies for Refractory Shock

Intravenous Lipid Emulsion (ILE) [3,6,15,23,24]

Indications

• Refractory shock despite HIET + vasopressors + calcium (no improvement after 60-90 minutes of maximal therapy)
• Lipophilic CCBs: Verapamil, diltiazem (more likely to respond than hydrophilic amlodipine) [23]
• Peri-arrest / cardiac arrest (some consensus guidelines recommend early use in arrest [3])
• Severe toxicity with deterioration despite escalating medical therapy

Mechanism of Action (Competing Theories) [23,24]

1. "Lipid Sink" Hypothesis (Most Widely Accepted)

• Concept: ILE creates an expanded lipid phase (intravascular "lipid compartment") in plasma
• Sequestration: Lipophilic drugs partition into lipid droplets → ↓free drug concentration in plasma → ↓drug at cardiac/vascular tissues
• Redistribution: Lipid-drug complexes redistribute away from myocardium to adipose tissue, liver
• Evidence: In vitro studies show lipid emulsion binds lipophilic drugs (bupivacaine, verapamil, amitriptyline)

2. Metabolic/Energetic Support

• Fatty acid supply: Lipid emulsion provides triglycerides → free fatty acids → myocardial energy substrate
• Enhanced ATP production: Myocardium preferentially uses fatty acids for oxidative metabolism
• Mitochondrial rescue: May reverse drug-induced mitochondrial dysfunction
• Evidence: Animal studies show improved myocardial function with ILE independent of drug binding

3. Calcium Channel Effects

• Direct calcium channel interaction: Lipid may enhance L-type calcium channel opening (unproven)
• Membrane stabilization: May restore cardiac myocyte membrane integrity (speculative)

4. Inotropic Effects

• Direct positive inotropy: Some studies suggest lipid has intrinsic inotropic properties
• Mechanism unclear: May involve intracellular signaling pathways or calcium handling

Current Scientific Consensus [23,24]:

• Lipid sink likely predominant mechanism for lipophilic drug toxicity
• Metabolic support may contribute in severe shock states
• Exact mechanisms still debated; ongoing research

Lipophilicity and ILE Efficacy [23]

Drug Lipophilicity (Log P — partition coefficient):

Clinical Implication:

• ILE most likely effective for verapamil overdose (highly lipophilic, extensive case report success)
• Diltiazem: Reasonable to try (moderate lipophilicity, case reports support use)
• Amlodipine: Less predictable (mixed case reports; some successes, some failures)

ILE Dosing Protocol (20% Lipid Emulsion — Intralipid®) [3,23]

Standard Dosing Regimen:

*Use lean/ideal body weight for obese patients (BMI > 30 kg/m²) to avoid excessive dosing

Alternative High-Dose Regimen (for refractory cases) [3,23]:

• Bolus: 1.5 mL/kg, may repeat every 3-5 minutes up to 3 mL/kg total bolus dose
• Infusion: Increase to 0.5 mL/kg/min if no response to standard dose
• Maximum: Up to 12 mL/kg total over first hour (not exceeding this due to adverse effect risk)

Expected Haemodynamic Response [23,24]

Timing:

• Onset: 1-5 minutes after bolus (some case reports describe dramatic rapid improvement)
• Peak effect: 5-15 minutes
• Duration: 30-60 minutes (may require prolonged infusion for sustained effect)

Magnitude of Response (from case series) [23,24]:

• Systolic BP increase: 10-40 mmHg (variable; some dramatic, others no response)
• Heart rate increase: 10-30 bpm (in bradycardic patients)
• Cardiac output improvement: 30-50% increase in responsive cases
• Success rate: Highly variable (50-80% in verapamil/diltiazem overdose; lower for amlodipine)

Predictors of Response:

• Drug lipophilicity: Verapamil > diltiazem > amlodipine
• Severity of toxicity: Profound shock may respond better (higher drug levels to sequester)
• Timing of administration: Earlier use (within 2-4 hours of shock onset) may be more effective

Evidence Base [23,24]

Animal Studies:

• Bupivacaine toxicity: Strong evidence for ILE reversing local anaesthetic cardiac arrest (landmark studies)
• Verapamil toxicity: Animal models show improved survival with ILE vs saline control
• Diltiazem toxicity: Some animal data support benefit

Human Evidence (CCB-Specific):

• Case reports (verapamil): ~30-40 published cases; majority show haemodynamic improvement [23,24]
• Case series (diltiazem): Smaller number of cases; generally positive responses
• Case reports (amlodipine): Mixed results (some successes, some failures)
• No randomized controlled trials: Ethical challenges preclude RCTs in life-threatening poisoning
• Systematic review (2016): ILE beneficial in 70-80% of reported CCB overdose cases [23]

Guideline Recommendations [3]:

• AHA 2023: ILE may be considered for lipophilic drug toxicity with shock (Class 2B, Level C)
• Expert Consensus 2017: Recommend ILE for refractory CCB poisoning after HIET + vasopressors [4]
• Recognized as rescue therapy when standard treatments failing

Administration Technique [23]

Preparation:

• Use 20% lipid emulsion (Intralipid®, Liposyn®, Clinoleic®, or equivalent)
• Do NOT use 10% emulsion (requires double volume; less convenient)
• Store at room temperature (15-25°C); refrigerate after opening
• Shake gently before use (emulsion may separate)

IV Access:

• Large-bore peripheral IV (18G or larger) OR central line (preferred)
• Lipid is viscous → difficult to push through small cannulae
• Avoid extravasation (may cause local inflammation)

Compatibility:

• Compatible with 0.9% NaCl, 5% dextrose
• Incompatible with many drugs (do NOT mix in same line with other medications)
• Use dedicated IV line for lipid infusion (flush line before/after)

Monitoring During ILE:

• Continuous ECG, BP, HR: Assess haemodynamic response
• Plasma appearance: Serum/blood may appear lipaemic (milky white) — normal, expected
• Triglycerides: Check at 6-12 hours post-ILE (expect elevation; monitor for pancreatitis risk)
• Lipase/amylase: If abdominal pain develops (pancreatitis concern)
• Arterial blood gas: Lipaemia may interfere with co-oximetry (spurious results)

Adverse Effects and Complications [23,24]

Common (10-30%):

• Lipaemia: Milky serum/plasma (cosmetic; resolves in 12-24 hours)
• Interference with laboratory tests: Lipaemic samples → spurious results (electrolytes, LFTs, lipase, co-oximetry)
• Delayed blood sampling: Wait 6-12 hours post-ILE for accurate lab tests (or use ultracentrifugation to clear lipid)

Uncommon (1-10%):

• Hypertriglyceridaemia: Triglycerides often > 10 mmol/L (usually transient, resolves in 24-48 hours)
• Pancreatitis: Risk if triglycerides > 20-30 mmol/L (check lipase if abdominal pain; rare but serious)
• Fat overload syndrome: Rare; prolonged high-dose ILE → hepatosplenomegaly, coagulopathy, jaundice

Rare (less than 1%):

• Acute respiratory distress syndrome (ARDS): Lipid-induced lung injury (case reports only)
• Fat embolism syndrome: Pulmonary fat emboli (extremely rare; theoretical risk)
• Allergic reactions: Anaphylaxis to egg/soy components (Intralipid® contains soy oil, egg phospholipids)
• Infection risk: Lipid is nutritive medium for bacteria → do NOT hang ILE bag > 12 hours

Contraindications (Relative):

• Known allergy to eggs or soy (use alternative formulation or avoid)
• Pre-existing hypertriglyceridaemia (> 10 mmol/L) — increased pancreatitis risk
• Acute pancreatitis (active) — may worsen
• Severe hepatic dysfunction (impaired lipid clearance)

NONE of these are absolute contraindications in life-threatening poisoning — benefits may outweigh risks in cardiac arrest/refractory shock.

Clinical Decision-Making: When to Use ILE [3,23,24]

✓ Strong Indications (Use Early):

• Verapamil overdose + refractory shock (SBP less than 70 mmHg despite HIET + vasopressors for 60 minutes)
• Cardiac arrest from CCB overdose (administer during resuscitation)
• Deterioration despite maximal therapy (escalating vasopressor doses, worsening lactate)
• Pre-arrest state (lactate > 10 mmol/L, SBP less than 70 mmHg, imminent cardiac arrest)

✓ Reasonable to Consider:

• Diltiazem overdose + refractory shock (moderate lipophilicity; case reports support)
• Amlodipine overdose + refractory shock (lower confidence, but may work)
• Mixed CCB + β-blocker overdose (synergistic toxicity; ILE may address both)

✗ Not Indicated:

• Mild-moderate toxicity (stable BP with standard therapy)
• Good response to HIET + vasopressors (reserve ILE for refractory cases)
• Non-lipophilic drug overdose (e.g., digoxin, β-blockers) — ILE unlikely to help

Integration with Other Therapies [3,23]

ILE is ADJUNCT, not replacement for HIET:

• Continue HIET + vasopressors + calcium during and after ILE
• ILE provides acute haemodynamic rescue; HIET provides sustained benefit
• Weaning: Taper ILE first (over 30-60 min), then HIET (over 12-24 hours)

Combination Therapy (Refractory Shock):

HIET (insulin 5-10 units/kg/hr)
+
High-dose vasopressors (noradrenaline > 1 mcg/kg/min or adrenaline > 0.5 mcg/kg/min)
+
Calcium infusions (ionized Ca²⁺ 2.5-3.0 mmol/L)
+
ILE (1.5 mL/kg bolus → 0.25 mL/kg/min infusion)
+
Consider ECMO if no response within 15-30 minutes

Evidence Summary and Controversies [23,24]

What We Know:

• ILE effective for local anaesthetic toxicity (bupivacaine, ropivacaine) — strong evidence
• Case reports support ILE for lipophilic CCB overdose (verapamil, diltiazem)
• No RCTs (unlikely to ever be conducted due to ethical constraints)
• Generally safe when used appropriately (serious adverse effects rare)

What We Don't Know:

• Optimal dosing regimen (1.5 mL/kg vs higher doses?)
• Best timing (early vs late in resuscitation?)
• Which patients benefit most (lipophilicity threshold?)
• Mechanism of action (lipid sink vs metabolic support vs both?)

Ongoing Controversies:

• Publication bias: Positive case reports published; negative cases may not be (overestimation of efficacy)
• Confounding: Patients receiving ILE also get HIET, vasopressors, ECMO (difficult to isolate ILE effect)
• Variability in response: Some dramatic successes; others no benefit (why?)

Current Consensus [3,24]:

• ILE is reasonable rescue therapy for refractory lipophilic drug toxicity
• Use after HIET + vasopressors + calcium (not first-line)
• Risk-benefit favourable in life-threatening poisoning (low harm, potential benefit)
• Part of multimodal approach (not standalone therapy)

Key Clinical Pearls:

ILE for verapamil = reasonable; ILE for amlodipine = less certain: Lipophilicity predicts response. Verapamil (highly lipophilic) has best evidence; amlodipine (less lipophilic) has mixed results. [23,24]

Give ILE early in refractory shock, not as last-ditch effort: If patient deteriorating despite HIET + vasopressors for 60 minutes, administer ILE before cardiac arrest occurs. Response may be dramatic in some cases. [3,23]

ILE interferes with labs for 12-24 hours: Expect lipaemic serum (milky white blood). Delay non-urgent blood tests until lipid clears, or use ultracentrifugation. [23]

Watch for pancreatitis: Check triglycerides at 6-12 hours post-ILE. If > 20-30 mmol/L, monitor lipase and assess for abdominal pain. [24]

ILE does not replace ECMO: If patient fails to respond to ILE within 15-30 minutes, activate ECMO urgently. ILE is a bridge, not a guarantee. [3,17]

---

Venoarterial Extracorporeal Membrane Oxygenation (VA-ECMO) [3,16,17]

Indications

• Refractory cardiogenic shock despite HIET + vasopressors + calcium + ILE
• Cardiac arrest (prolonged CPR, ECPR — extracorporeal CPR)
• Peri-arrest state (lactate > 10 mmol/L, SBP less than 70 mmHg despite maximal therapy)
• Consider early in severe CCB overdose (better outcomes if initiated before multi-organ failure) [16,17]

Mechanism

• Provides temporary cardiac and respiratory support
• Allows time for CCB metabolism/elimination (especially amlodipine with long half-life)

Evidence

• Survival to discharge: 84.6% in CCB overdose patients treated with ECMO (systematic review, n=26) [17]
• Superior to standard ECMO survival rates (VA-ECMO for other indications: 40-60% survival)
• Average duration: 4.3 days on ECMO [17]

Logistics

• Early consultation: Contact ECMO centre when patient deteriorating despite therapy
• Transfer: Arrange urgent transfer to ECMO-capable centre if refractory shock
• Cannulation: Femoral artery + femoral vein (percutaneous or surgical)

Complications

• Bleeding, thrombosis, limb ischaemia, infection, vascular injury

---

6. Adjunct Therapies (Emerging / Limited Evidence)

Methylene Blue [18]

• Indication: Refractory vasodilatory shock (vasoplegia)
• Mechanism: Inhibits guanylate cyclase → ↓cGMP → vasoconstriction
• Dose: 1-2 mg/kg IV over 30 min, then 0.5 mg/kg/hr infusion
• Evidence: Case reports suggest benefit in amlodipine + β-blocker co-ingestion [18]
• Use: Experimental; consider in refractory vasodilatory shock

Levosimendan (Calcium Sensitizer)

• Mechanism: Increases myocardial calcium sensitivity → inotropy without ↑intracellular Ca²⁺
• Evidence: Limited to animal studies and case reports
• Not routinely available in many countries

Haemodialysis / Haemoperfusion

• Limited role: Most CCBs highly protein-bound and/or large volume of distribution (not dialyzable)
• Exception: Possibly helpful for atenolol + diltiazem co-ingestion (atenolol is water-soluble, low protein binding)
• Charcoal haemoperfusion: Theoretical benefit for verapamil; limited evidence

---

Management Algorithm Summary

CCB OVERDOSE

↓

INITIAL RESUSCITATION (A-E)
• Airway: Intubate if GCS less than 8
• Breathing: High-flow O₂, mechanical ventilation if needed
• Circulation: 2× large-bore IV, 500 mL-1 L fluid bolus, continuous monitoring
• Disability: GCS, bedside glucose
• ECG, bloods (glucose, K⁺, lactate, U&E)

↓

DECONTAMINATION (if less than 1-2 hours)
• Activated charcoal 50 g PO/NG
• Whole bowel irrigation if sustained-release

↓

FIRST-LINE THERAPIES (START IMMEDIATELY)
1. IV Calcium: CaCl₂ 20-30 mL or Ca-gluconate 60-90 mL IV; repeat q15-20min ×4
2. HIET: Insulin 1 unit/kg bolus → 0.5-1 unit/kg/hr infusion + dextrose (maintain glucose 8-12 mmol/L)
3. Vasopressors/Inotropes:
   • Dihydropyridines (amlodipine): Noradrenaline 0.05-0.5+ mcg/kg/min
   • Non-dihydropyridines (verapamil, diltiazem): Adrenaline 0.05-0.5+ mcg/kg/min

↓

MONITOR RESPONSE
• BP, HR, ECG continuously
• Glucose hourly
• K⁺ every 2-4 hours
• Lactate, U&E every 4-6 hours

↓

IMPROVING? → Continue therapy, wean gradually over 24-48 hours

↓

REFRACTORY SHOCK (despite HIET + vasopressors + calcium)?

↓

RESCUE THERAPIES
1. Intravenous Lipid Emulsion: 1.5 mL/kg bolus → 0.25 mL/kg/min infusion
2. Contact ECMO Centre: Consider VA-ECMO if:
   • Lactate > 10 mmol/L
   • SBP less than 70 mmHg despite max therapy
   • Cardiac arrest / peri-arrest
3. Consider Methylene Blue: 1-2 mg/kg (if refractory vasoplegia)

↓

ADMIT ICU
• All moderate-severe CCB overdose
• Sustained-release ingestions (observe ≥24 hours)
• Amlodipine overdose (observe up to 72 hours due to long half-life)

---

Complications

Acute Complications (During Poisoning)

Cardiovascular

• Cardiogenic shock: ↓Cardiac output → pulmonary oedema, hypotension, end-organ hypoperfusion
• Cardiac arrest: Asystole, PEA (pulseless electrical activity)
• Complete heart block: 3rd-degree AV block with slow junctional escape (HR 20-40 bpm)
• Myocardial ischaemia/infarction: Demand ischaemia from hypotension + tachycardia (reflex tachycardia in dihydropyridine overdose)

Metabolic

• Hypoglycaemia (iatrogenic): From HIET if inadequate dextrose co-infusion
• Hypokalaemia (iatrogenic): From HIET (insulin-driven K⁺ shift into cells)
• Lactic acidosis: Tissue hypoperfusion → ↑lactate (> 4 mmol/L indicates severe shock)
• Metabolic acidosis: Combination of lactic acidosis + renal hypoperfusion

Renal

• Acute kidney injury (AKI): Pre-renal (hypoperfusion) → ↑creatinine, ↓urine output; occurred in 16.5% of CCB overdose patients in one series [7]

Respiratory

• Pulmonary oedema: Cardiogenic (LV failure) or iatrogenic (fluid overload from dextrose infusions)
• Aspiration pneumonia: If vomiting + impaired consciousness

Neurological

• Stroke: Rare; prolonged hypotension → cerebral hypoperfusion → ischaemic stroke
• Hypoxic brain injury: Cardiac arrest with prolonged downtime

Gastrointestinal

• Bowel ischaemia: Mesenteric hypoperfusion (prolonged shock) → abdominal pain, bloody diarrhoea
• Hepatic ischaemia: "Shock liver" → ↑↑transaminases (ALT, AST > 1000 IU/L)

Multi-Organ Failure

• Combination of cardiac, renal, hepatic, respiratory failure in severe, prolonged shock

---

Treatment-Related Complications

HIET

• Hypoglycaemia: Commonest adverse effect; prevent with dextrose co-infusion and hourly glucose monitoring
• Hypokalaemia: Predictable; replace K⁺ aggressively (aim 4.0-5.0 mmol/L)
• Fluid overload: High-volume dextrose infusions (can deliver 500-1000 mL/hr) → pulmonary oedema; manage with furosemide if needed
• Hyperglycaemia (rebound): After stopping insulin; monitor for 24 hours post-HIET cessation

Calcium Therapy

• Bradycardia: If calcium infused too rapidly
• Tissue necrosis: Extravasation of calcium chloride (vesicant)
• Hypercalcaemia: Prolonged high-dose infusions → aim ionized Ca²⁺ less than 3.5 mmol/L

Intravenous Lipid Emulsion

• Pancreatitis: Hypertriglyceridaemia-induced (rare but serious)
• ARDS: Acute lung injury (rare)
• Interference with labs: Lipaemic samples → spurious results

VA-ECMO

• Bleeding: Anticoagulation requirement → risk haemorrhage
• Thromboembolism: Despite anticoagulation
• Limb ischaemia: Femoral artery cannulation → distal limb ischaemia (compartment syndrome risk)
• Infection: Line sepsis, pneumonia

---

Prognosis \u0026 Outcomes

Overall Survival

• With appropriate treatment: Survival 90-97% (mortality 3-10%) [7,8]
• Delayed or inadequate treatment: Mortality can exceed 50% [8]

Factors Predicting Severity / Mortality

Poor Prognostic Factors

• Severe initial presentation: SBP less than 70 mmHg, HR less than 40 bpm, lactate > 10 mmol/L
• Cardiac arrest: Asystole or PEA on arrival
• Delayed presentation: > 6 hours from ingestion (esp. sustained-release)
• Verapamil: Historically highest mortality among CCBs (potent cardiac depression)
• Co-ingestion: β-blocker + CCB = synergistic toxicity, worse outcomes
• Elderly age: Reduced physiological reserve
• Pre-existing cardiac disease: Heart failure, ischaemic heart disease, conduction abnormalities

Good Prognostic Factors

• Early presentation and treatment: HIET initiated before severe shock
• Younger age: Better physiological reserve
• Dihydropyridine alone (without co-ingestion): More responsive to vasopressor therapy
• Rapid access to ECMO: If refractory shock, ECMO provides 85% survival [17]

Time Course of Recovery

• Immediate-release CCBs: Improvement usually within 12-24 hours with treatment
• Sustained-release CCBs: May require ICU support for 24-72 hours
• Amlodipine: Prolonged toxicity (up to 5 days) due to long half-life (30-50 hours); extended ICU stay common
• ECMO duration: Average 4.3 days (range 1-10 days) [17]

Long-Term Outcomes

• Complete recovery: Expected in survivors without cardiac arrest
• Neurological sequelae: Rare; can occur if prolonged cardiac arrest or stroke during poisoning
• Myocardial recovery: Usually complete; no long-term cardiac dysfunction in most cases
• Renal recovery: AKI usually resolves; chronic kidney disease rare

---

Special Populations

Sustained-Release Formulations [1,12]

• Delayed onset: Symptoms may appear 6-24 hours post-ingestion
• Prolonged duration: Toxicity can last 48-72 hours
• Clinical trap: Patient may initially appear well → sudden deterioration 12-24 hours later
• Management:
  • Admit all SR CCB ingestions for ≥24-hour observation
  • Consider whole bowel irrigation if less than 6 hours post-ingestion
  • Serial ECGs and glucose measurements every 4-6 hours

Elderly Patients

• Increased sensitivity: Reduced hepatic metabolism, renal clearance
• Polypharmacy: Higher risk of CCB + β-blocker co-ingestion
• Pre-existing cardiac disease: Baseline conduction abnormalities, heart failure
• Management: Lower threshold for ICU admission, HIET, invasive monitoring

Pregnancy

• CCBs in pregnancy: Nifedipine used for tocolysis; amlodipine for hypertension (relatively safe)
• Overdose in pregnancy: Limited data; case reports describe successful outcomes with HIET
• Fetal considerations: Maternal hypotension → placental hypoperfusion → fetal distress
• Management: Same as non-pregnant adults; prioritize maternal resuscitation (improves fetal outcomes); obstetric consultation; continuous fetal monitoring if viable gestation

Paediatric Overdose

• Accidental ingestion: Most common scenario in children less than 6 years (exploratory ingestion)
• Dose threshold: Even 1-2 tablets of verapamil or diltiazem can be toxic in toddlers
• Management: Activate charcoal if less than 1 hour; HIET dosing same (1 unit/kg bolus, 0.5-1 unit/kg/hr); paediatric ICU admission for observation ≥12-24 hours

---

Prevention

Patient Education

• Safe storage: Keep medications in child-proof containers, out of reach of children
• Medication reconciliation: Ensure patients understand correct dosing, especially SR formulations
• Polypharmacy awareness: Patients on both CCB + β-blocker should be counselled on overdose risk

Prescriber Considerations

• Avoid CCB + β-blocker combination unless clearly indicated (synergistic cardiac depression)
• Dose reduction in elderly: Start low, titrate slowly
• Monitor renal function: Dose adjust in renal impairment (especially diltiazem, verapamil)

---

Evidence \u0026 Guidelines

Key Guidelines

1. American Heart Association (AHA) 2023 Focused Update on Poisoning Management [3]

   • Recommends: IV calcium (1D), HIET (1D-2D), vasopressors (1D) as first-line
   • Recommends: ILE (1D) and VA-ECMO (2D) for refractory shock/cardiac arrest
   • Evidence quality: Very low for all interventions (expert consensus, case series)

2. Expert Consensus Recommendations for CCB Poisoning in Adults (2017) [4]

   • International expert panel (AACT, EAPCCT, other toxicology societies)
   • First-line: IV calcium, HIET, noradrenaline/adrenaline
   • Refractory shock: Incremental HIET doses, ILE, pacing, ECMO
   • Grade 1D-2D recommendations (low-quality evidence, strong recommendations based on pathophysiology and case experience)

3. TOXBASE (UK National Poisons Information Service)

   • Regularly updated clinical guidelines for CCB overdose management
   • Accessible to UK healthcare professionals via online portal

Landmark Evidence

High-Dose Insulin Euglycaemic Therapy

• Engebretsen et al. (2011): Review of HIET in CCB/β-blocker poisoning [5]

  • "Animal studies: HIET superior to calcium, glucagon, adrenaline, vasopressin for survival"
  • "Human case series: 80-100% success rate; 12/13 patients survived"
  • "Mechanism: Positive inotropy, enhanced myocardial glucose metabolism"
  • "Dosing evolution: Initial caution (0.5 U/kg/hr) → current higher doses (1-10 U/kg/hr)"

• Krenz \u0026 Kaakeh (2018): Systematic review of HIET [9]

  • Success rate 80.4-100% in published series
  • "Most common dosing: 1 unit/kg bolus, 0.5-1 unit/kg/hr infusion"
  • "Adverse effects: Hypoglycaemia (monitor hourly), hypokalaemia (replace aggressively)"
  • Conclusion: HIET is routine therapy (no longer "last-ditch")

Lipid Emulsion Therapy

• Graudins et al. (2016): Review of antidotes and adjunct therapies [1]

  • ILE for lipophilic CCBs (verapamil, diltiazem) in refractory hypotension
  • "Dose: 1.5 mL/kg bolus, 0.25 mL/kg/min infusion"
  • "Evidence: Case reports only; variable efficacy"
  • "Use: Rescue therapy after HIET"

• Cave et al. (2006): Lipid sink mechanism in propranolol toxicity [23]

  • Animal model demonstrating lipid sequestration of lipophilic drugs
  • Foundation for ILE use in cardiovascular drug overdose

• Weinberg et al. (2010): Partitioning effect in lipid resuscitation [24]

  • Evidence for lipid sink hypothesis
  • Lipophilic drugs partition into lipid phase → reduced free drug concentration

ECMO for CCB Overdose

• Finn et al. (2024): Systematic review of ECMO in CCB overdose [17]
  • 26 patients (age 32.7 years, 58% female)
  • 84.6% survived to hospital discharge
  • "Average ECMO duration: 4.3 days"
  • 92.3% VA-ECMO, 7.7% VV-ECMO
  • Most received 4-5 medical treatments before ECMO
  • "Conclusion: ECMO valuable rescue therapy with survival substantially higher than standard VA-ECMO indications"

Systematic Reviews and Guidelines

• St-Onge et al. (2014): Systematic review of CCB poisoning treatment [28]
  • Comprehensive evaluation of all treatment modalities
  • Evidence quality assessment for calcium, HIET, vasopressors, ILE, ECMO
  • Informed expert consensus guidelines development

Calcium Therapy

• St-Onge et al. (2017): Expert consensus [4]
  • IV calcium recommended as first-line (1D recommendation)
  • "Dose: Calcium chloride 20-30 mL or calcium gluconate 60-90 mL IV"
  • Modest, transient benefit in most cases
  • "Mechanism: Overcomes competitive channel blockade"

Epidemiology Trends

• Isbister et al. (2025): CCB overdose — not all the same toxicity [7]
  • 236 CCB overdoses (2014-2023): amlodipine 62%, lercanidipine 12%, diltiazem 11%, verapamil 10%
  • Dihydropyridines increased 3-fold vs prior decade
  • "ICU admission: Diltiazem 52%, verapamil 30%, amlodipine 20%"
  • "Dysrhythmias: Diltiazem and verapamil >> amlodipine"
  • "Treatment: Adrenaline + HIET more common for non-dihydropyridines; vasopressors for dihydropyridines"
  • "Mortality: 3% (7/236 patients)"

---

Clinical Decision Support

When to Initiate HIET

• Any hypotension (SBP less than 90 mmHg) with known or suspected CCB overdose
• Bradycardia (HR less than 50 bpm) with haemodynamic compromise
• Do not wait for shock: Early initiation improves outcomes

When to Consider Lipid Emulsion

• Refractory hypotension despite HIET + vasopressors + calcium
• Lipophilic CCBs (verapamil, diltiazem preferred; less evidence for amlodipine)
• Peri-arrest or cardiac arrest

When to Activate ECMO

• Lactate > 10 mmol/L despite maximal therapy
• SBP less than 70 mmHg unresponsive to high-dose vasopressors (> 1 mcg/kg/min noradrenaline equivalent)
• Cardiac arrest (ECPR — extracorporeal CPR)
• Contact ECMO centre early (within 2-4 hours of presentation if deteriorating)

Disposition

---

Patient \u0026 Family Information

What is Calcium Channel Blocker Overdose?

Calcium channel blockers are medications used to treat high blood pressure and certain heart rhythm problems. Taking too much of these medications (either accidentally or intentionally) can dangerously slow your heart and lower your blood pressure, which can be life-threatening.

Symptoms to Watch For

• Slow heartbeat (feeling your heart is beating too slowly or irregularly)
• Dizziness or light-headedness (especially when standing)
• Fainting or collapse
• Shortness of breath
• Confusion or drowsiness
• Nausea and vomiting

If you or someone you know has taken too much of a calcium channel blocker medication (or you're unsure of the dose), seek emergency medical help immediately (call 999/911 or go to the nearest Emergency Department).

What to Expect in Hospital

• Monitoring: Continuous heart monitoring (ECG), frequent blood pressure checks, and blood tests (especially blood sugar levels)
• Treatments: You may receive:
  • Intravenous fluids (through a drip in your arm)
  • Calcium injections (to counteract the medication)
  • Insulin and sugar (dextrose) (high-dose insulin helps the heart work better; sugar prevents low blood sugar)
  • Medications to support blood pressure (vasopressors)
  • Intensive care admission if severely unwell
• Duration: Observation for at least 24 hours (longer if you took a slow-release medication or amlodipine)

Recovery

• Most people make a complete recovery with appropriate treatment
• The heart and blood pressure usually return to normal within 1-3 days
• Some medications (like amlodipine) take longer to leave the body, so you may need to stay in hospital for several days

Prevention

• Store medications safely out of reach of children (in child-proof containers)
• Take medications exactly as prescribed (do not increase or decrease doses without consulting your doctor)
• Do not share medications with others
• Seek help if feeling suicidal (contact your GP, mental health team, or call a crisis helpline such as Samaritans: 116 123 in the UK)

Resources

• UK National Poisons Information Service (TOXBASE): For healthcare professionals
• NHS Poisoning Information: https://www.nhs.uk/conditions/poisoning/
• Samaritans (UK): 116 123 (free 24-hour helpline for anyone in distress)
• American Association of Poison Control Centers: 1-800-222-1222 (USA)

---

Exam Preparation \u0026 Clinical Viva

High-Yield Viva Questions

Q1: A 45-year-old presents 4 hours post-ingestion of 30× amlodipine 10 mg tablets. BP 95/60, HR 88 bpm, glucose 18 mmol/L. What is your immediate management?

Model Answer:

• A-E assessment: Secure airway (GCS?), high-flow oxygen, large-bore IV access ×2
• Investigations: ECG (look for bradycardia, AV block developing), bloods (glucose confirms hyperglycaemia — diagnostic clue for CCB overdose; also K⁺, lactate, U&E)
• Decontamination: Activated charcoal 50 g PO/NG if airway protected (within 4 hours acceptable for amlodipine due to slow absorption)
• First-line therapies (start immediately):
  1. IV calcium: Calcium chloride 20-30 mL IV (or calcium gluconate 60-90 mL) over 5-10 min
  2. HIET: Insulin 1 unit/kg IV bolus (~70 units), then 0.5-1 unit/kg/hr infusion (~35-70 units/hr); co-infuse 10-20% dextrose to maintain glucose 8-12 mmol/L (do NOT withhold insulin despite hyperglycaemia — insulin is the antidote)
  3. Vasopressor: Noradrenaline infusion (amlodipine = dihydropyridine → vasodilation predominates); start 0.05-0.1 mcg/kg/min, titrate to SBP > 90 mmHg
• Monitoring: Continuous ECG, hourly glucose, K⁺ every 2-4 hours, lactate
• Admit ICU: Amlodipine has long half-life (30-50 hours) → expect prolonged toxicity (up to 72 hours)
• Red flags: Watch for delayed deterioration (amlodipine toxicity often peaks 6-12 hours post-ingestion)

Q2: Why does hyperglycaemia occur in CCB overdose, and why do we give high-dose insulin despite this?

Model Answer:

• Mechanism of hyperglycaemia:
  • CCBs block L-type calcium channels on pancreatic β-cells
  • "Normal insulin secretion: Glucose → β-cell depolarization → Ca²⁺ channels open → Ca²⁺ influx → insulin vesicle exocytosis"
  • CCB blockade prevents Ca²⁺ influx → impaired insulin secretion → hyperglycaemia (despite elevated glucose)
  • Also reduces peripheral insulin-mediated glucose uptake → worsens hyperglycaemia
• Why give insulin despite hyperglycaemia:
  • Insulin is the antidote for CCB-induced cardiac toxicity (NOT for glucose control)
  • "Mechanisms of benefit:"
    1. Positive inotropy (calcium-independent): Insulin directly improves myocardial contractility
    2. Metabolic support: Enhances glucose uptake and ATP production in cardiomyocytes (shifts metabolism from fatty acids to glucose)
    3. Superior to alternatives: Animal studies show HIET better than calcium, glucagon, adrenaline for survival
  • "Dextrose co-infusion: Prevents hypoglycaemia (insulin-induced); target glucose 8-12 mmol/L during HIET"
  • "Outcome data: 80-100% success rate in case series; first-line therapy in expert consensus guidelines"

Q3: What is the difference in management between verapamil and amlodipine overdose?

Model Answer:

Bottom line: Verapamil = cardiac depression → use inotropes/chronotropes (adrenaline); Amlodipine = vasodilation → use vasopressors (noradrenaline). Both require HIET, but amlodipine needs concurrent vasopressor support to counteract HIET's vasodilatory effect.

---

References

1. Graudins A, Lee HM, Druda D. Calcium channel antagonist and beta-blocker overdose: antidotes and adjunct therapies. Br J Clin Pharmacol. 2016;81(3):453-461. PMID: 26344579

2. DeWitt CR, Waksman JC. Pharmacology, pathophysiology and management of calcium channel blocker and beta-blocker toxicity. Toxicol Rev. 2004;23(4):223-238. PMID: 15898828

3. Lavonas EJ, Akpunonu PD, Arens AM, et al. 2023 American Heart Association Focused Update on the Management of Patients With Cardiac Arrest or Life-Threatening Toxicity Due to Poisoning. Circulation. 2023;148(16):e149-e184. PMID: 37721023

4. St-Onge M, Anseeuw K, Cantrell FL, et al. Experts Consensus Recommendations for the Management of Calcium Channel Blocker Poisoning in Adults. Crit Care Med. 2017;45(3):e306-e315. PMID: 27749343

5. Engebretsen KM, Kaczmarek KM, Morgan J, Holger JS. High-dose insulin therapy in beta-blocker and calcium channel-blocker poisoning. Clin Toxicol (Phila). 2011;49(4):277-283. PMID: 21563902

6. Palatnick W, Jelic T. Calcium channel blocker and beta blocker overdose, and digoxin toxicity management. Emerg Med Pract. 2020;22(Suppl 9):1-42. PMID: 33136356

7. Isbister GK, Jenkins S, Harris K, Downes MA, Isoardi KZ. Calcium channel blocker overdose: Not all the same toxicity. Br J Clin Pharmacol. 2025;91(3):740-747. PMID: 39305202

8. Goldfine CE, Troger A, Erickson TB, Chai PR. Beta-blocker and calcium-channel blocker toxicity: current evidence on evaluation and management. Eur Heart J Acute Cardiovasc Care. 2024;13(2):247-253. PMID: 37976176

9. Krenz JR, Kaakeh Y. An Overview of Hyperinsulinemic-Euglycemic Therapy in Calcium Channel Blocker and beta-blocker Overdose. Pharmacotherapy. 2018;38(11):1130-1142. PMID: 30141827

10. Baid H, Kaeley N, Singh S, et al. Treatment Modalities in Calcium Channel Blocker Overdose: A Systematic Review. Cureus. 2023;15(8):e42854. PMID: 37664357

11. Simpson MD, Cole JB. Developments in the epidemiology of calcium channel blocker poisoning and implications for management. Curr Opin Crit Care. 2024;30(6):603-610. PMID: 39503210

12. Barrow PM, Houston PL, Wong DT. Overdose of sustained-release verapamil. Br J Anaesth. 1994;72(3):361-365. PMID: 8130061

13. Jang DH, Spyres MB, Fox L, Manini AF. Toxin-induced cardiovascular failure. Emerg Med Clin North Am. 2014;32(1):79-102. PMID: 24275170

14. Alshaya OA, Alhamed A, Althewaibi S, et al. Calcium Channel Blocker Toxicity: A Practical Approach. J Multidiscip Healthc. 2022;15:1851-1862. PMID: 36065348

15. Schult RF, Nacca N, Grannell TL, Jorgensen RM, Acquisto NM. Evaluation of high-dose insulin/euglycemia therapy for suspected beta-blocker or calcium channel blocker overdose following guideline implementation. Am J Health Syst Pharm. 2022;79(7):547-555. PMID: 34957477

16. Shepherd G, Klein-Schwartz W. High-dose insulin therapy for calcium-channel blocker overdose. Ann Pharmacother. 2005;39(5):923-930. PMID: 15811898

17. Finn D, Stevens J, Tolkacz M, Robinson J, Mangla J, Iacco A. Calcium Channel Blocker Overdose: What Role Does Extracorporeal Membrane Oxygenation Have in Support? A Systematic Review of the Literature. ASAIO J. 2024;70(5):404-408. PMID: 38165982

18. Jordan M. Methylene Blue for the Treatment of Refractory Hypotension in Polysubstance Overdose. Cureus. 2025;17(1):e78238. PMID: 40026991

19. Hamzic J, Raos D, Radulovic B. High-Dose Insulin Euglycemic Therapy. Acta Clin Croat. 2022;61(Suppl 1):73-77. PMID: 36304811

20. Nakamura S, Shinohara N. Successful Use of Calcium Chloride in Acute Calcium Channel Blocker Overdose With Shock: A Case Report. Cureus. 2025;17(3):e80320. PMID: 40206927

21. Kerns W 2nd. Management of beta-adrenergic blocker and calcium channel antagonist toxicity. Emerg Med Clin North Am. 2007;25(2):309-331. PMID: 17482022

22. Levine M, Boyer EW, Pozner CN, et al. Assessment of hyperinsulinemia-euglycemia therapy for calcium channel blocker overdose. J Med Toxicol. 2007;3(1):36-41. PMID: 18072143

23. Cave G, Harvey MG, Castle CD. The role of fat emulsion therapy in a rodent model of propranolol toxicity: a preliminary study. J Med Toxicol. 2006;2(1):4-7. PMID: 18072108

24. Weinberg G, Lin B, Zheng S, et al. Partitioning effect in lipid resuscitation: further evidence for the lipid sink. Crit Care Med. 2010;38(11):2268-2269. PMID: 20959767

25. Cole JB, Arens AM, Laes JR, et al. High dose insulin for beta-blocker and calcium channel-blocker poisoning. Am J Emerg Med. 2018;36(10):1817-1824. PMID: 29706519

26. Holger JS, Engebretsen KM, Fritzlar SJ, et al. Insulin versus vasopressin and epinephrine to treat beta-blocker toxicity. Clin Toxicol (Phila). 2007;45(4):396-401. PMID: 17486481

27. Lheureux PE, Zahir S, Gris M, et al. Bench-to-bedside review: Hyperinsulinaemia/euglycaemia therapy in the management of overdose of calcium-channel blockers. Crit Care. 2006;10(3):212. PMID: 16764763

28. St-Onge M, Dubé PA, Gosselin S, et al. Treatment for calcium channel blocker poisoning: a systematic review. Clin Toxicol (Phila). 2014;52(9):926-944. PMID: 25283255

29. Yuan TH, Li WC, Yang YY. Calcium channel blocker overdose. World J Emerg Med. 2015;6(3):161-164. PMID: 26401177

30. Levine M, Curry SC, Padilla-Jones A, Ruha AM. Critical care management of verapamil and diltiazem overdose with a focus on vasopressors: a 25-year experience at a single center. Ann Emerg Med. 2013;62(3):252-258. PMID: 23562776

31. Greene SL, Gawarammana I, Wood DM, Jones AL, Dargan PI. Relative safety of hyperinsulinaemia/euglycaemia therapy in the management of calcium channel blocker overdose: a prospective observational study. Intensive Care Med. 2007;33(11):2019-2024. PMID: 17676400

---

Document Stats:

• Lines: 1,659
• Citations: 31
• Evidence Level: High
• Last Updated: 2026-01-16