Analgesics and antipyretics — formative SAQs · Paeds SAQs

Prompt

SAQ 1 tests the weight-based calculation of a paracetamol and ibuprofen dose with the adult ceiling, the position on alternating the two agents, and the safety boundaries of aspirin avoidance and the codeine and tramadol restriction. SAQ 2 tests the recognition and immediate management of a suspected paracetamol overdose in a young child, including the time of ingestion, the four-hour paracetamol level on the treatment nomogram, and the N-acetylcysteine decision.

SAQ 1 — A febrile, uncomfortable preschool child

Question 1 — 10 formative marks; suggested time 15 minutes [2]

A 4-year-old girl weighing 16 kg is brought in with a fever of 39.4 °C and a sore throat. She is alert, drinking small amounts and mildly uncomfortable, with no features of toxicity. The registrar asks you to prescribe her analgesia and antipyretia and to advise the family. [2]

State the weight-based dose, frequency and maximum daily dose for paracetamol in this child, and the adult maximum single and daily doses that cap the calculation. (3 marks)
State the weight-based dose, frequency, maximum daily dose and age and weight criteria for ibuprofen. (2 marks)
The family ask whether they should "just alternate paracetamol and ibuprofen every two hours." Give the correct position, citing the evidence and the safety rationale. (3 marks)
Name the two analgesic and antipyretic safety restrictions the registrar must respect in a febrile child of this age, and one discharge safety-net. (2 marks) [1] [6]

Full-credit answer — SAQ 1

Reveal full-credit answer for SAQ 1

1. Paracetamol dose

Paracetamol is dosed at 15 mg per kg per dose, every four to six hours, to a maximum of 60 mg per kg per day. For this 16 kg child, one dose is 15 multiplied by 16, which is 240 mg per dose (rounded to an available formulation). The adult maximum is 1 g per dose and 4 g per day, and the calculation is capped there; this child's calculated daily maximum of 960 mg per day is below the 4 g adult ceiling, but the cap is checked explicitly. [2]

2. Ibuprofen dose

Ibuprofen is dosed at 5 to 10 mg per kg per dose, every six to eight hours, to a maximum of 30 mg per kg per day. For this 16 kg child, one dose is 80 to 160 mg (rounded sensibly). Ibuprofen is used from three months of age and over 5 kg, in a child who is drinking and passing urine and with no contraindication (dehydration, renal impairment, bleeding risk, aspirin-sensitive asthma). [2]

3. The alternating question

Routine alternating of paracetamol and ibuprofen is not recommended. The 2024 network meta-analysis found that short-term dual therapy can lower temperature modestly faster and for longer than either agent alone, but the effect is modest and dual therapy increases the risk of dosing error, parental confusion and doubled or exceeded doses. The defensible position is a single effective agent with a clear written plan first, reserving dual therapy for a distressed child who has not responded to monotherapy, with a written dosing schedule, the maximum daily dose stated, and a dosing syringe. Always ask what the child has already been given, because the commonest ceiling breach is a second preparation the carer did not realise contained paracetamol. [1] [2]

4. Safety restrictions and discharge safety-net

First, aspirin is avoided in children under 16 with viral illness because of the association with Reye syndrome; use paracetamol or ibuprofen. Second, codeine and tramadol are contraindicated in children under 12 and after tonsillectomy or adenoidectomy, because a CYP2D6 ultrarapid metaboliser converts the prodrug to a fatal morphine overdose; this child's mild pain does not require an opioid, but the restriction governs any escalation. The discharge safety-net names the features that should bring the child back urgently: reduced feeding, reduced wet nappies, lethargy or drowsiness, a fever that does not settle, a non-blanching rash, or difficulty breathing. [6] [7]

SAQ 2 — A suspected paracetamol overdose

Question 2 — 10 formative marks; suggested time 15 minutes [4]

A 3-year-old boy weighing 14 kg is brought in 90 minutes after drinking an unknown volume of his sibling's paracetamol suspension. The bottle is empty and the ingestion was witnessed. He is alert and looks well. [4]

State the immediate clinical actions in the first hour, including the single most important historical fact to establish. (2 marks)
State which investigation is taken, when it is taken, and how the result is interpreted. (3 marks)
State the drug used for treatment, its mechanism, and the loading dose by the ANZ protocol. (3 marks)
Give two situations in which treatment is started regardless of the level, and one prognostic statement. (2 marks) [4] [5]

Full-credit answer — SAQ 2

Reveal full-credit answer for SAQ 2

1. Immediate actions

Assess the airway, breathing and circulation; the child is alert and well at present but is monitored. Stop any further paracetamol. The single most important historical fact to establish is the time of ingestion, because the paracetamol level is interpreted on the treatment nomogram against time, and without a time the level is uninterpretable and the clinician errs toward treating. Establish whether the ingestion was a single event or staggered over time, and estimate the milligrams ingested from the bottle if possible. [4]

2. The investigation

A serum paracetamol level is taken at or after four hours post-ingestion and plotted on the treatment nomogram against the time of ingestion. A level on or above the treatment line triggers N-acetylcysteine. A level drawn before four hours is uninterpretable for the nomogram. Because this child presented at 90 minutes, the level is not yet due; it is taken at the four-hour mark. Liver function tests and a coagulation screen are taken as baseline and to detect early hepatotoxicity. [4]

3. The treatment

The treatment is N-acetylcysteine, which works by replenishing glutathione and directly detoxifying the reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI), thereby preventing hepatocyte necrosis. By the ANZ protocol, it is given as a 150 mg per kg intravenous loading dose over the first hour, followed by the weight-banded maintenance regimen. It is highly effective when given early, which is why the early window is the treatable window. [4] [5]

4. Treat regardless of the level, and prognosis

Treatment is started regardless of the level when the ingestion is staggered over time, when the time of ingestion is unknown, when a large ingestion is clearly documented, or when there is any clinical or biochemical evidence of hepatotoxicity. The prognosis is excellent when N-acetylcysteine is given within the early window; the injury is largely preventable. Delay, staggered ingestion that depletes glutathione before the level is interpretable, or late presentation with established coagulopathy and encephalopathy shift the prognosis toward acute liver failure, and the liver-transplant service is involved early in a deteriorating child. [4] [5]

References

[1]De la Cruz-Mena, J E; López-González, E; López-López, M J; et al. Short-term Dual Therapy or Mono Therapy With Acetaminophen and Ibuprofen for Fever: A Network Meta-Analysis Pediatrics, 2024.PMID 39318339
[2]Paul, I M; Yestraan, J; McGuire, K; et al. Acetaminophen and ibuprofen in the treatment of pediatric fever: a narrative review Curr Med Res Opin, 2021.PMID 33966545
[4]Chiew, A L; Fountain, J S; Greig, R; et al. Updated guidelines for the management of paracetamol poisoning in Australia and New Zealand Med J Aust, 2020.PMID 31786822
[5]Chiew, A L; Gluud, C; Brok, J; Buckley, N A Interventions for paracetamol (acetaminophen) overdose Cochrane Database Syst Rev, 2018.PMID 29473717
[6]Schrör, K Aspirin and Reye syndrome: a review of the evidence Paediatr Drugs, 2007.PMID 17523700
[7]Kohler, J E; Downard, C D; Heiss, K F; et al. Continued Prescribing of Periprocedural Codeine and Tramadol to Children after a Black Box Warning J Surg Res, 2020.PMID 32693330
[11]Pillai Riddell, R; Yamada, J; Harrison, D; et al. Non-pharmacological management of infant and young child procedural pain Cochrane Database Syst Rev, 2023.PMID 37314064
[12]Parikh, J M; Turner, R; Tang, A; Baehner, F An update on the safety of prescribing opioids in pediatrics Expert Opin Drug Saf, 2019.PMID 30650988