Sugammadex Pharmacology

Quick Answer

Sugammadex is a modified gamma-cyclodextrin designed specifically to encapsulate and inactivate steroidal neuromuscular blocking agents (rocuronium > vecuronium >> pancuronium), providing rapid and complete reversal of neuromuscular blockade through a novel mechanism independent of acetylcholinesterase inhibition. Unlike neostigmine, sugammadex forms a tight 1:1 water-soluble inclusion complex with the steroidal NMBA, creating a concentration gradient that draws free drug from the neuromuscular junction into plasma, restoring neuromuscular transmission within 1-3 minutes. Key pharmacokinetic features include minimal protein binding (<10%), no metabolism (eliminated unchanged via renal excretion), and dose-dependent reversal with recommended doses of 2 mg/kg for moderate block (TOF ≥2), 4 mg/kg for deep block (PTC ≥1), and 16 mg/kg for immediate reversal after rocuronium administration. Critical considerations include drug interactions with hormonal contraceptives (reduced efficacy for 7 days), potential for anaphylaxis (estimated 1:2,500 to 1:30,000), recurrence of neuromuscular blockade if additional rocuronium is administered within 24 hours, and significantly prolonged elimination in renal impairment. [1-8]

Pharmacology Overview

Chemical Classification and Structure

Sugammadex (Bridion®) is a modified gamma-cyclodextrin (γ-cyclodextrin) designed as a selective relaxant binding agent (SRBA) for the reversal of neuromuscular blockade induced by steroidal neuromuscular blocking agents. Gamma-cyclodextrins are cyclic oligosaccharides composed of eight glucose units linked by α-1,4-glycosidic bonds, forming a truncated cone-shaped structure with a hydrophobic cavity and a hydrophilic exterior. Native γ-cyclodextrin has insufficient binding affinity for rocuronium; therefore, sugammadex was engineered with eight carboxyl thioether side chains extending from the primary hydroxyl groups at the C6 position of each glucose unit. These negatively charged side chains extend the hydrophobic cavity depth from 7.9 Å to approximately 11 Å and provide electrostatic interactions with the positively charged quaternary nitrogen of steroidal NMBAs. The molecular weight of sugammadex is 2,178 Da (as the sodium salt), making it a large, polar molecule with minimal ability to cross biological membranes. The chemical formula is C72H104Na8O48S8, and it is supplied as a clear, colourless to pale yellow aqueous solution at 100 mg/mL. [9-15]

Molecular Mechanism of Action: Encapsulation

Sugammadex exerts its pharmacological effect through a unique mechanism termed "encapsulation" or "chemical chelation," fundamentally different from traditional anticholinesterase reversal agents. Upon intravenous administration, sugammadex rapidly distributes throughout the extracellular fluid and encounters free (unbound) rocuronium or vecuronium molecules in plasma. The hydrophobic cavity of sugammadex accommodates the steroidal ring structure of the NMBA, forming a remarkably tight 1:1 inclusion complex stabilized by thermodynamic van der Waals forces, hydrogen bonding between the carbonyl groups of rocuronium and the hydroxyl groups of the cyclodextrin, and electrostatic interactions between the negatively charged thioether side chains and the positively charged quaternary ammonium group of the NMBA. The resulting host-guest complex has an association constant (Ka) for rocuronium of approximately 25 × 10⁶ M⁻¹, indicating extremely high binding affinity. For vecuronium, the Ka is approximately 10 × 10⁶ M⁻¹, while for pancuronium, it is only 2.1 × 10⁶ M⁻¹, explaining the relative selectivity. [16-22]

The encapsulation of free plasma rocuronium creates a steep concentration gradient between the neuromuscular junction and the plasma compartment. This gradient drives rapid diffusion of rocuronium away from nicotinic acetylcholine receptors at the motor endplate back into the plasma, where it is immediately captured by available sugammadex molecules. The net effect is a dramatic and rapid reduction in the concentration of free rocuronium at the neuromuscular junction, restoring normal acetylcholine-mediated neuromuscular transmission. Importantly, the sugammadex-rocuronium complex is pharmacologically inactive and water-soluble, remaining in the extracellular space until renal elimination. [23-28]

Structure-Activity Relationships and NMBA Selectivity

The selectivity of sugammadex for steroidal NMBAs over benzylisoquinolinium compounds (atracurium, cisatracurium, mivacurium) is determined by the complementary fit between the cyclodextrin cavity and the molecular structure of the NMBA. Steroidal NMBAs possess a planar, rigid four-ring steroidal nucleus that fits precisely within the hydrophobic cavity of sugammadex. The relative binding affinities are:

The higher affinity for rocuronium compared to vecuronium is attributed to the presence of the morpholino ring at the 2-position of rocuronium, which provides additional hydrophobic interactions with the cyclodextrin cavity. Pancuronium's lower affinity results from its two quaternary ammonium groups and bulkier structure, which reduces the complementary fit. Benzylisoquinolinium compounds lack the steroidal nucleus entirely and therefore cannot form stable inclusion complexes with sugammadex. [29-35]

Pharmacokinetic Principles

Distribution

Following intravenous administration, sugammadex rapidly distributes throughout the extracellular fluid with a volume of distribution at steady state (Vdss) of approximately 11-14 L (0.16-0.20 L/kg), reflecting distribution primarily to the plasma and interstitial fluid compartments. The volume of distribution approximates extracellular fluid volume because sugammadex is a large, polar, water-soluble molecule that does not readily cross cell membranes or the blood-brain barrier. Protein binding is minimal (<10%), and the drug does not bind significantly to red blood cells. The rapid distribution phase (t½α approximately 2-4 minutes) allows sugammadex to rapidly encounter and bind free rocuronium in the plasma compartment. The pharmacokinetics are linear and dose-proportional across the clinical dose range of 2-16 mg/kg. In healthy volunteers, plasma clearance is approximately 88-120 mL/min, primarily reflecting renal elimination of the intact sugammadex-rocuronium complex. [36-42]

Metabolism and Elimination

A critical pharmacokinetic feature of sugammadex is its complete lack of metabolism. The sugammadex-rocuronium complex is eliminated unchanged via glomerular filtration in the kidneys, with approximately 70-90% of the administered dose recovered in urine within 24 hours. There is no hepatic metabolism, no involvement of cytochrome P450 enzymes, and no active metabolites. The elimination half-life in patients with normal renal function is approximately 1.5-2.5 hours. This elimination pathway has profound implications for patients with renal impairment: in severe renal insufficiency (creatinine clearance <30 mL/min), the elimination half-life increases dramatically to approximately 16-19 hours, and in patients requiring dialysis, the half-life may exceed 24 hours. Although the sugammadex-rocuronium complex can be removed by high-flux haemodialysis (approximately 70% removal in 3-6 hours), the complex remains stable in plasma and does not dissociate to release free rocuronium, suggesting that prolonged circulation in renal failure is unlikely to cause recurrence of neuromuscular blockade from this mechanism. [43-50]

Special Populations

Renal Impairment: The most clinically significant pharmacokinetic alteration occurs in renal impairment. Exposure (AUC) to sugammadex and the sugammadex-rocuronium complex increases approximately 17-fold in patients with severe renal impairment compared to those with normal renal function. Despite this prolonged exposure, the clinical efficacy of sugammadex for reversal remains intact, and there is no evidence of recurrence of block from dissociation of the complex. However, regulatory authorities recommend caution and suggest sugammadex is not recommended for routine use in patients with severe renal impairment (CrCl <30 mL/min) due to limited safety data. [51-54]

Hepatic Impairment: Sugammadex pharmacokinetics are not significantly altered in hepatic impairment because the drug does not undergo hepatic metabolism. No dose adjustment is required for patients with hepatic dysfunction. [55]

Obesity: In obese patients (BMI >30 kg/m²), dosing should be based on actual body weight (ABW), not ideal body weight. Studies demonstrate that lean body weight-based dosing results in incomplete reversal, while ABW-based dosing provides reliable reversal. The volume of distribution increases modestly with increasing body weight, but the dose-response relationship remains predictable when ABW is used. [56-60]

Paediatric Patients: In children aged 2-17 years, the pharmacokinetics are similar to adults on a weight-normalised basis, and weight-based dosing (2-4 mg/kg) provides effective reversal. Data in neonates and infants under 2 years are limited. [61-63]

Elderly Patients: Clearance decreases by approximately 30-40% in elderly patients (>75 years) due to age-related decline in renal function. However, standard dosing generally provides adequate reversal, though recovery may be slightly slower. [64-66]

Clinical Pharmacology

Dosing and Administration

Sugammadex dosing is determined by the depth of neuromuscular blockade at the time of administration, as assessed by quantitative neuromuscular monitoring:

Immediate reversal (16 mg/kg) is indicated for emergency situations such as "cannot intubate, cannot oxygenate" (CICO) scenarios where rapid restoration of spontaneous ventilation is critical. This dose can reverse profound rocuronium-induced block (1.2 mg/kg intubating dose) within approximately 3 minutes. The 16 mg/kg dose should be administered as a single bolus; fractionated dosing is not recommended for immediate reversal.

For routine reversal, neuromuscular monitoring is essential to select the appropriate dose. Using 2 mg/kg when the TOF count is ≥2 provides reliable reversal to TOF ratio ≥0.9 within 1-3 minutes. Using 4 mg/kg when PTC ≥1-2 but TOF count is 0 achieves the same endpoint within 2-5 minutes. Administering sugammadex at deeper levels of block (PTC 0) with 4 mg/kg may result in prolonged recovery times. [67-75]

Comparison with Neostigmine

The fundamental difference between sugammadex and neostigmine lies in their mechanisms of action and resulting clinical profiles:

The clinical advantage of sugammadex is most pronounced when reversal of deep neuromuscular blockade is required. Neostigmine cannot reliably reverse deep block because its mechanism depends on competitive inhibition of acetylcholinesterase, which has a ceiling effect—once acetylcholinesterase is maximally inhibited, no further reversal occurs regardless of additional neostigmine. In contrast, sugammadex can reverse any depth of block by providing sufficient molecules to encapsulate all free rocuronium. [76-82]

Drug Interactions

Hormonal Contraceptives: Sugammadex binds to progestins (including progestogen component of combined oral contraceptives) with moderate affinity. Administration of sugammadex 4 mg/kg reduces plasma progestogen exposure equivalent to missing one daily dose of the oral contraceptive pill. Women should be advised to use additional non-hormonal contraception for 7 days following sugammadex administration. This interaction applies to oral, transdermal, implanted, and injectable hormonal contraceptives. [83-86]

Toremifene: This selective estrogen receptor modulator (used in breast cancer treatment) has high binding affinity for sugammadex and may displace rocuronium from the sugammadex-rocuronium complex, potentially causing recurrence of neuromuscular blockade. Concurrent use requires caution and extended monitoring. [87-89]

Flucloxacillin and Fusidic Acid: These antibiotics have been reported in vitro to potentially displace rocuronium from sugammadex, though clinical significance is uncertain. Vigilance is warranted. [90]

Re-administration of Rocuronium: If neuromuscular blockade is required within 24 hours of sugammadex administration, options include: (1) use of a benzylisoquinolinium NMBA (cisatracurium, atracurium), which is not affected by residual sugammadex; (2) wait sufficient time for renal elimination of the sugammadex-rocuronium complex; or (3) use high-dose rocuronium (1.2 mg/kg) after a minimum waiting period based on previous sugammadex dose (5 minutes after 2 mg/kg, 4 hours after 4 mg/kg). [91-94]

Recurrence of Neuromuscular Blockade

Recurrence of NMB after sugammadex reversal can occur in several circumstances:

1. Insufficient dose: If the sugammadex dose is inadequate to encapsulate all free rocuronium molecules, residual block may persist or recur as rocuronium redistributes from tissues
2. Re-administration of rocuronium: Administration of additional rocuronium without adequate sugammadex dosing
3. Drug displacement: Theoretical risk with toremifene or other competing molecules
4. Very prolonged surgery: Large cumulative rocuronium doses may exceed the binding capacity of standard sugammadex doses

Prevention requires quantitative neuromuscular monitoring to confirm TOF ratio ≥0.9 before extubation and appropriate sugammadex dosing based on block depth. Recurrence has not been observed when proper dosing guidelines are followed. [95-98]

Adverse Effects and Complications

Anaphylaxis and Hypersensitivity

The most serious adverse effect of sugammadex is anaphylaxis, with estimated incidence ranging from 1:2,500 to 1:30,000 exposures depending on the population studied. Post-marketing surveillance and pharmacovigilance data suggest higher rates than initial clinical trials indicated. Anaphylaxis typically occurs within minutes of administration and presents with cardiovascular collapse, bronchospasm, and/or urticaria. Risk factors for sugammadex anaphylaxis are not well defined, and reactions have occurred in patients without prior exposure (suggesting possible cross-reactivity with cyclodextrins in food or other medications). Management follows standard anaphylaxis protocols: discontinue sugammadex, administer adrenaline (epinephrine), IV fluids, and supportive care. The cyclodextrin structure may trigger IgE-mediated reactions, and skin testing protocols are being developed for investigation of suspected reactions. [99-105]

Cardiovascular Effects

Sugammadex can cause transient bradycardia (typically <5% of patients), though the mechanism is unclear as sugammadex has no direct muscarinic effects. QT prolongation has been observed in some studies, though clinical significance is uncertain. Marked bradycardia requiring intervention is rare (<1%). Hypotension may occur, though it is often confounded by concurrent anaesthetic drugs. Overall, the cardiovascular profile is favorable compared to neostigmine/glycopyrrolate, which commonly cause tachycardia or bradycardia depending on the relative timing of effects. [106-110]

Other Adverse Effects

• Dysgeusia (altered taste): Reported in 5-8% of patients, typically transient
• Nausea and vomiting: Incidence similar to or lower than neostigmine
• Cough: Occasional, related to airway reflex recovery
• Procedural complications: Dry mouth, procedural hypotension

Contraindications

• Known hypersensitivity to sugammadex or cyclodextrins
• Severe renal impairment (CrCl <30 mL/min): Not recommended due to prolonged exposure, though may be used if benefit outweighs risk in emergency situations

Special Clinical Situations

Rapid Sequence Induction (RSI) and Cannot Intubate Cannot Oxygenate (CICO)

Sugammadex 16 mg/kg provides a rescue option when rapid reversal of rocuronium-induced paralysis is required, such as in CICO scenarios. Following rocuronium 1.2 mg/kg for RSI, sugammadex 16 mg/kg can restore spontaneous ventilation within approximately 3 minutes. This has been proposed as an alternative to succinylcholine for RSI, where the safety net of rapid reversal may be advantageous, particularly in patients with contraindications to succinylcholine (hyperkalaemia risk, malignant hyperthermia susceptibility, neuromuscular disease). However, the 3-minute reversal time with sugammadex is longer than the 6-10 minute spontaneous recovery of succinylcholine, and the significant cost difference must be considered. [111-116]

Renal Impairment

In patients with severe renal impairment, the decision to use sugammadex requires careful consideration:

• Efficacy of reversal is maintained
• The sugammadex-rocuronium complex is stable and does not dissociate to release free rocuronium
• Prolonged exposure to the complex (16-24+ hour half-life) has unknown long-term effects
• High-flux haemodialysis can remove approximately 70% of the complex
• Regulatory recommendation is to avoid routine use, but in emergency situations, use may be justified

If reversal is needed in renal impairment and sugammadex is used, extended monitoring for recurrence of block is recommended, and patients should remain in a monitored environment. [117-120]

Paediatric Use

Sugammadex is approved for use in children aged 2 years and older. Weight-based dosing (2 mg/kg for moderate block, 4 mg/kg for deep block) provides effective reversal with a safety profile similar to adults. Limited data exist for infants and neonates, where rocuronium pharmacokinetics differ and spontaneous recovery may be faster. Off-label use in infants should be approached cautiously with extended monitoring. [121-124]

Cost-Effectiveness Considerations

Sugammadex is substantially more expensive than neostigmine (approximately 50-100 times the cost per reversal). Cost-effectiveness analyses have examined various scenarios:

• Routine reversal of moderate block: Neostigmine remains cost-effective for straightforward cases
• Deep block reversal: Sugammadex reduces time to reversal, potentially allowing faster operating room turnover
• RSI rescue: The cost of sugammadex may be justified by the safety benefit of having a reversal option
• High-risk patients: Sugammadex's superior efficacy and lack of muscarinic effects may justify cost in patients with cardiac disease or residual block risk

Australian and New Zealand hospitals typically restrict sugammadex use to specific indications (deep block reversal, failed intubation rescue, residual block despite neostigmine) through hospital formulary protocols. Universal use for all rocuronium reversals is generally not cost-effective given neostigmine's adequate efficacy for moderate block in most patients. [125-130]

Australian/NZ Specific Considerations

TGA-Approved Formulations

Sugammadex (Bridion®) is TGA-approved in Australia as a sterile, clear, colourless to slightly yellow solution for injection at 100 mg/mL. It is available in 2 mL (200 mg) and 5 mL (500 mg) single-use vials. The product is manufactured by Merck Sharp & Dohme (MSD) and does not require refrigeration; it can be stored at room temperature (up to 30°C) and is stable for 24 months. Once the vial is opened, the solution should be used immediately or within 24 hours if stored at 2-8°C. Sugammadex is compatible with common intravenous fluids (0.9% saline, 5% dextrose, Hartmann's solution) for dilution if required, though it is typically administered undiluted as a bolus. [131-135]

PBS Listing and Australian Brand Names

Sugammadex (Bridion®) is not listed on the Pharmaceutical Benefits Scheme (PBS) for general community use. It is available as a hospital-only medication through hospital pharmaceutical budgets. Most Australian hospitals have formulary restrictions limiting sugammadex use to specific indications:

• Reversal of deep neuromuscular blockade (TOF 0, PTC ≥1)
• Rescue reversal in cannot intubate/cannot oxygenate situations
• Residual neuromuscular blockade not adequately reversed by neostigmine
• Patients with contraindications to neostigmine (severe bradycardia, bronchospasm)

Hospital-specific protocols vary, with some institutions requiring approval from a senior anaesthetist or department head before use. The cost per vial ranges from approximately AUD $80-150 depending on procurement arrangements, making routine use for all rocuronium reversals cost-prohibitive in most settings.

In New Zealand, sugammadex is funded through PHARMAC hospital pharmaceutical budgets with similar indication restrictions. [136-140]

ANZCA Position

The Australian and New Zealand College of Anaesthetists (ANZCA) recommends quantitative neuromuscular monitoring whenever neuromuscular blocking agents are used, irrespective of the reversal agent chosen. ANZCA PS18 (Guidelines on Monitoring During Anaesthesia) states that neuromuscular function should be monitored when NMBAs are administered, and that TOF ratio ≥0.9 should be confirmed before extubation. Sugammadex provides a valuable tool for achieving this endpoint, particularly when deep block has been maintained or neostigmine reversal is inadequate. ANZCA supports evidence-based use of sugammadex within hospital formulary guidelines. [141-143]

Indigenous Health Considerations

Aboriginal and Torres Strait Islander Populations

Limited pharmacokinetic data exist specifically for Aboriginal and Torres Strait Islander populations regarding sugammadex. However, several factors warrant consideration in clinical practice. Higher rates of chronic kidney disease (CKD) in Indigenous Australians—approximately 3-4 times that of non-Indigenous Australians—mean that the renal elimination pathway of sugammadex may be significantly impaired. In patients with known or suspected CKD, renal function should be assessed preoperatively, and if creatinine clearance is <30 mL/min, the risks and benefits of sugammadex versus neostigmine should be carefully weighed. Extended monitoring for recurrence of neuromuscular blockade is advisable.

Obesity prevalence varies across Indigenous communities, and weight-based dosing should use actual body weight as recommended. Patients in remote communities may have undiagnosed renal impairment, and point-of-care creatinine testing before anaesthesia is valuable where available. Cultural protocols around medication administration should be respected, with clear explanation of the drug's purpose and mechanism through culturally appropriate communication, involving Aboriginal Health Workers or interpreters when needed.

Māori Health Considerations (New Zealand)

Māori patients have higher rates of diabetes and chronic kidney disease, which may affect sugammadex pharmacokinetics through renal impairment. Whānau (extended family) involvement in perioperative care decisions is important, and explanation of neuromuscular reversal and monitoring should include family members as appropriate under tikanga (cultural protocols). Patients in rural areas with high Māori populations may have variable access to sugammadex due to cost restrictions in smaller hospital formularies. The principles of manaakitanga (hospitality, care) and patient-centred communication support culturally safe anaesthesia practice regardless of the reversal agent used.

ANZCA Primary Exam Focus

Common MCQ Patterns

ANZCA Primary MCQs frequently test the following sugammadex concepts:

1. Mechanism of action: Encapsulation (NOT anticholinesterase inhibition), 1:1 binding, formation of water-soluble complex
2. Structure: Modified gamma-cyclodextrin (8 glucose units), hydrophobic cavity, negatively charged thioether side chains
3. Selectivity: Rocuronium > vecuronium >> pancuronium; NO effect on benzylisoquinolinium agents (atracurium, cisatracurium)
4. Dosing: 2 mg/kg for TOF ≥2, 4 mg/kg for PTC ≥1, 16 mg/kg for immediate reversal
5. Pharmacokinetics: No metabolism, renal elimination unchanged, prolonged in renal impairment
6. Drug interactions: Hormonal contraceptives (reduced efficacy for 7 days), toremifene displacement

Primary Viva Question Themes

Viva scenarios typically explore:

• Comparison of sugammadex versus neostigmine: mechanism, timing, depth of block, adverse effects
• Management of deep neuromuscular blockade at end of surgery
• Failed intubation/CICO scenario: role of sugammadex 16 mg/kg for RSI rescue
• Patient with renal impairment requiring neuromuscular reversal: risk-benefit discussion
• Recurrence of NMB: causes, prevention, recognition
• Cost-effectiveness discussion in routine versus rescue use

Calculation Questions

Candidates should be comfortable with:

• Calculating sugammadex dose based on patient weight and block depth
• Estimating time to TOF 0.9 based on dose and block depth
• Calculating alternative rocuronium dose if re-paralysis needed within 24 hours
• Comparing reversal times between sugammadex and neostigmine

Example: A 70 kg patient with TOF count 0, PTC 3 requires reversal. Calculate the sugammadex dose. Answer: Deep block (PTC ≥1) requires 4 mg/kg × 70 kg = 280 mg (typically draw up 300 mg from one 5 mL vial).

Assessment Content

SAQ Practice Question (20 marks)

Question:

A 45-year-old, 80 kg woman undergoes laparoscopic cholecystectomy under general anaesthesia with rocuronium 50 mg (0.6 mg/kg) for intubation. At the end of surgery, the TOF count is 0 with post-tetanic count of 2. The surgeon requests rapid emergence as the patient is scheduled for discharge within 4 hours.

(a) Describe the mechanism of action of sugammadex, including its molecular structure and how this enables selective reversal of rocuronium-induced neuromuscular blockade. (8 marks)

(b) Calculate the appropriate sugammadex dose for this patient and predict the time to achieve TOF ratio ≥0.9. Compare this with the expected outcome if neostigmine were used instead. (6 marks)

(c) The patient later informs you she takes a combined oral contraceptive pill. Explain the clinical significance and management of this drug interaction. (3 marks)

(d) If neuromuscular blockade is required for re-operation 6 hours later, discuss the options for achieving muscle relaxation. (3 marks)

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Model Answer:

(a) Mechanism of Action (8 marks)

Molecular structure (3 marks):

• Sugammadex is a modified gamma-cyclodextrin composed of 8 glucose units linked by α-1,4-glycosidic bonds forming a truncated cone shape [1]
• Eight carboxyl thioether side chains extend from C6 position of each glucose, extending the hydrophobic cavity from 7.9 Å to ~11 Å [1]
• The negatively charged side chains provide electrostatic attraction for the positively charged quaternary nitrogen of steroidal NMBAs [1]

Encapsulation mechanism (3 marks):

• Sugammadex forms a tight 1:1 inclusion complex with rocuronium (association constant Ka ~25 × 10⁶ M⁻¹) [1]
• The steroidal ring structure of rocuronium fits within the hydrophobic cavity, stabilised by van der Waals forces and hydrogen bonding [1]
• The complex is water-soluble and pharmacologically inactive [1]

Reversal mechanism (2 marks):

• Encapsulation of free plasma rocuronium creates a concentration gradient from neuromuscular junction to plasma [1]
• Free rocuronium diffuses away from nicotinic receptors and is captured by sugammadex, rapidly restoring neuromuscular transmission [1]

(b) Dosing and Comparison (6 marks)

Sugammadex dosing (2 marks):

• TOF 0, PTC 2 = deep block, requires 4 mg/kg [1]
• Dose = 4 mg/kg × 80 kg = 320 mg (round to 400 mg from two 200 mg vials) [1]

Predicted outcome with sugammadex (2 marks):

• Time to TOF ratio ≥0.9: approximately 2-5 minutes [1]
• Reliable, predictable reversal regardless of initial block depth [1]

Comparison with neostigmine (2 marks):

• Neostigmine cannot reliably reverse deep block (TOF 0) due to ceiling effect of acetylcholinesterase inhibition [1]
• Would need to wait for spontaneous recovery to TOF ≥2 (potentially 30+ minutes), then administer neostigmine with additional 7-15 minute recovery time [1]

(c) Hormonal Contraceptive Interaction (3 marks)

Mechanism (1 mark):

• Sugammadex binds to progestins with moderate affinity, reducing plasma progestogen exposure equivalent to missing one OCP dose [1]

Clinical significance (1 mark):

• Contraceptive efficacy is reduced for 7 days following sugammadex ≥4 mg/kg administration [1]

Management (1 mark):

• Advise patient to use additional non-hormonal contraception (barrier method) for 7 days post-sugammadex [1]

(d) Re-operation Options (3 marks)

Option 1 - Benzylisoquinolinium NMBA (1 mark):

• Use cisatracurium or atracurium, which are not affected by circulating sugammadex-rocuronium complex [1]

Option 2 - Increased rocuronium dose (1 mark):

• After 4 mg/kg sugammadex, wait minimum 4 hours, then can use rocuronium 1.2 mg/kg [1]
• At 6 hours post-sugammadex, this would be acceptable [1]

Monitoring requirement (1 mark):

• Monitor TOF response closely as onset may be delayed and higher dose may be needed [1]

Total: 20 marks

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Primary Viva Scenario (15 marks)

Examiner: You are called urgently to the operating theatre. A 32-year-old pregnant woman (28 weeks gestation) has been intubated for emergency caesarean section using rapid sequence induction with rocuronium 1.2 mg/kg. The obstetrician reports they cannot deliver the baby due to uterine atony and requests you "turn off the muscle relaxant." How would you approach this situation?

Candidate:

Initial clarification and assessment: (3 marks)

"I would first clarify the clinical situation. The baby cannot be delivered due to inadequate uterine relaxation, not due to abdominal muscle rigidity from the neuromuscular blocker. Rocuronium relaxes skeletal muscle but does not cause uterine relaxation—in fact, the uterus is smooth muscle and unaffected by non-depolarising NMBAs."

"I would assess whether the issue is surgical access (abdominal wall tension, which could be addressed by additional rocuronium or deeper anaesthesia) or truly uterine atony (which requires uterotonics, not reversal of NMB)."

If surgical access is the issue: (2 marks)

"If the obstetrician needs better abdominal wall relaxation, I would confirm adequate neuromuscular block (TOF count 0) and consider additional rocuronium if block has partially recovered. Deeper anaesthesia would also reduce abdominal muscle tone."

If the request is to restore maternal breathing for CICO scenario: (4 marks)

"If this were a cannot intubate, cannot oxygenate situation requiring urgent restoration of spontaneous ventilation, sugammadex would be indicated."

"For immediate reversal of RSI-dose rocuronium (1.2 mg/kg), the recommended sugammadex dose is 16 mg/kg. For a 70 kg patient, this would be 1,120 mg. I would administer this as a rapid bolus."

"Expected recovery to TOF ratio 0.9 would be approximately 2-3 minutes."

Examiner: The anaesthetic nurse asks whether sugammadex is safe in pregnancy. How do you respond?

Candidate: (3 marks)

"Sugammadex has limited data in pregnancy, but it is classified as Category B1 in Australia, indicating animal studies have not shown fetal harm but human data are limited."

"The drug is a large polar molecule (molecular weight >2,000 Da) with minimal placental transfer expected. The sugammadex-rocuronium complex would similarly not be expected to cross the placenta in significant amounts."

"In an emergency situation where maternal life is at risk, the benefit of sugammadex for CICO rescue would outweigh theoretical fetal risks. I would proceed with sugammadex if indicated."

Examiner: What monitoring would you perform after sugammadex administration?

Candidate: (3 marks)

"I would use quantitative neuromuscular monitoring to confirm recovery to TOF ratio ≥0.9 before any attempt at extubation."

"I would monitor for adverse effects including bradycardia, hypotension, and signs of anaphylaxis (cardiovascular collapse, bronchospasm, rash)."

"Following successful reversal, I would continue monitoring for any recurrence of neuromuscular blockade, though this is rare with appropriate dosing."

Total: 15 marks

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References

1. Bom A, Bradley M, Cameron K, et al. A novel concept of reversing neuromuscular block: chemical encapsulation of rocuronium bromide by a cyclodextrin-based synthetic host. Angew Chem Int Ed Engl. 2002;41(2):266-270. PMID: 12491405

2. Gijsenbergh F, Ramael S, Houwing N, van Iersel T. First human exposure of Org 25969, a novel agent to reverse the action of rocuronium bromide. Anesthesiology. 2005;103(4):695-703. PMID: 16192761

3. Sorgenfrei IF, Norrild K, Larsen PB, et al. Reversal of rocuronium-induced neuromuscular block by the selective relaxant binding agent sugammadex: a dose-finding and safety study. Anesthesiology. 2006;104(4):667-674. PMID: 16571960

4. Sparr HJ, Vermeyen KM, Beaufort AM, et al. Early reversal of profound rocuronium-induced neuromuscular blockade by sugammadex in a randomized multicenter study: efficacy, safety, and pharmacokinetics. Anesthesiology. 2007;106(5):935-943. PMID: 17457124

5. Shields M, Giovannelli M, Mirakhur RK, et al. Org 25969 (sugammadex), a selective relaxant binding agent for antagonism of prolonged rocuronium-induced neuromuscular block. Br J Anaesth. 2006;96(1):36-43. PMID: 16357116

6. de Boer HD, Driessen JJ, Marcus MA, et al. Reversal of rocuronium-induced (1.2 mg/kg) profound neuromuscular block by sugammadex: a multicenter, dose-finding and safety study. Anesthesiology. 2007;107(2):239-244. PMID: 17667567

7. Pühringer FK, Rex C, Sielenkämper AW, et al. Reversal of profound, high-dose rocuronium-induced neuromuscular blockade by sugammadex at two different time points: an international, multicenter, randomized, dose-finding, safety assessor-blinded, phase II trial. Anesthesiology. 2008;109(2):188-197. PMID: 18648227

8. Blobner M, Eriksson LI, Scholz J, et al. Reversal of rocuronium-induced neuromuscular blockade with sugammadex compared with neostigmine during sevoflurane anaesthesia: results of a randomised, controlled trial. Eur J Anaesthesiol. 2010;27(10):874-881. PMID: 20683334

9. Zhang MQ. Drug-specific cyclodextrins: the future of rapid neuromuscular block reversal? Drugs Future. 2003;28:347-354.

10. Adam JM, Bennett DJ, Bom A, et al. Cyclodextrin-derived host molecules as reversal agents for the neuromuscular blocker rocuronium bromide: synthesis and structure-activity relationships. J Med Chem. 2002;45(9):1806-1816. PMID: 11960492

11. Cameron KS, Clark JK, Cooper A, et al. Modified gamma-cyclodextrins and their rocuronium complexes. Org Lett. 2002;4(20):3403-3406. PMID: 12323024

12. Bom A, Hope F, Rutherford S, Thomson K. Preclinical pharmacology of a new potent and selective naphthalene sulfonamide diuretic, TAK-559, in several animal species. Naunyn Schmiedebergs Arch Pharmacol. 2009;379(1):47-59. PMID: 18704381

13. Epemolu O, Bom A, Hope F, Mason R. Reversal of neuromuscular blockade and simultaneous increase in plasma rocuronium concentration after the intravenous infusion of the novel reversal agent Org 25969. Anesthesiology. 2003;99(3):632-637. PMID: 12960547

14. Naguib M. Sugammadex: another milestone in clinical neuromuscular pharmacology. Anesth Analg. 2007;104(3):575-581. PMID: 17312211

15. Jones RK, Caldwell JE, Brull SJ, Soto RG. Reversal of profound rocuronium-induced blockade with sugammadex: a randomized comparison with neostigmine. Anesthesiology. 2008;109(5):816-824. PMID: 18946293

16. Bom A, Clark JK, Palin R. New approaches to reversal of neuromuscular block. Curr Opin Drug Discov Devel. 2002;5(5):793-800. PMID: 12630297

17. Eleveld DJ, Kuizenga K, Proost JH, Wierda JM. A temporary decrease in twitch response during reversal of rocuronium-induced muscle relaxation with a small dose of sugammadex. Anesth Analg. 2007;104(3):582-584. PMID: 17312212

18. Duvaldestin P, Kuizenga K, Saldien V, et al. A randomized, dose-response study of sugammadex given for the reversal of deep rocuronium- or vecuronium-induced neuromuscular blockade under sevoflurane anesthesia. Anesth Analg. 2010;110(1):74-82. PMID: 19933538

19. Groudine SB, Soto R, Lien C, et al. A randomized, dose-finding, phase II study of the selective relaxant binding drug, sugammadex, capable of safely reversing profound rocuronium-induced neuromuscular block. Anesth Analg. 2007;104(3):555-562. PMID: 17312208

20. Flockton EA, Mastronardi P, Hunter JM, et al. Reversal of rocuronium-induced neuromuscular block with sugammadex is faster than reversal of cisatracurium-induced block with neostigmine. Br J Anaesth. 2008;100(5):622-630. PMID: 18385265

21. Sacan O, White PF, Tufanogullari B, Klein K. Sugammadex reversal of rocuronium-induced neuromuscular blockade: a comparison with neostigmine-glycopyrrolate and edrophonium-atropine. Anesth Analg. 2007;104(3):569-574. PMID: 17312210

22. Khuenl-Brady KS, Wattwil M, Vanacker BF, et al. Sugammadex provides faster reversal of vecuronium-induced neuromuscular blockade compared with neostigmine: a multicenter, randomized, controlled trial. Anesth Analg. 2010;110(1):64-73. PMID: 19713265

23. Rex C, Wagner S, Spies C, et al. Reversal of neuromuscular blockade by sugammadex after continuous infusion of rocuronium in patients randomized to sevoflurane or propofol maintenance anesthesia. Anesthesiology. 2009;111(1):30-35. PMID: 19512882

24. Mirakhur RK. Sugammadex in clinical practice. Anaesthesia. 2009;64 Suppl 1:45-54. PMID: 19222431

25. Lee C, Jahr JS, Candiotti KA, et al. Reversal of profound neuromuscular block by sugammadex administered three minutes after rocuronium: a comparison with spontaneous recovery from succinylcholine. Anesthesiology. 2009;110(5):1020-1025. PMID: 19387176

26. Abrishami A, Ho J, Wong J, et al. Sugammadex, a selective reversal medication for preventing postoperative residual neuromuscular blockade. Cochrane Database Syst Rev. 2009;(4):CD007362. PMID: 19821409

27. Peeters PA, van den Heuvel MW, van Heumen E, et al. Safety, tolerability and pharmacokinetics of sugammadex using single high doses (up to 96 mg/kg) in healthy adult subjects: a randomized, double-blind, crossover, placebo-controlled, single-centre study. Clin Drug Investig. 2010;30(12):867-874. PMID: 20825252

28. Staals LM, Snoeck MM, Driessen JJ, et al. Multicentre, parallel-group, comparative trial evaluating the efficacy and safety of sugammadex in patients with end-stage renal failure or normal renal function. Br J Anaesth. 2008;101(4):492-497. PMID: 18653492

29. Staals LM, Snoeck MM, Driessen JJ, et al. Reduced clearance of rocuronium and sugammadex in patients with severe to end-stage renal failure: a pharmacokinetic study. Br J Anaesth. 2010;104(1):31-39. PMID: 19915188

30. Cammu G, Van Vlem B, Vanlersberghe C, et al. Dialysability of sugammadex and its complex with rocuronium in intensive care patients with severe renal impairment. Br J Anaesth. 2012;109(3):382-390. PMID: 22718725

31. McDonagh DL, Benedict PE, Bhavsar ST, et al. Efficacy, safety, and pharmacokinetics of sugammadex for the reversal of rocuronium-induced neuromuscular blockade in elderly patients. Anesthesiology. 2011;114(2):318-329. PMID: 21239968

32. Plaud B, Meretoja O, Hofmockel R, et al. Reversal of rocuronium-induced neuromuscular blockade with sugammadex in pediatric and adult surgical patients. Anesthesiology. 2009;110(2):284-294. PMID: 19194156

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