Paeds SAQs · clinical-pharmacology-and-therapeutics
Opioids and acute pain medicines — formative SAQs
Two MedVellum formative short-answer questions on opioids and acute pain medicines in children: recognising why codeine and tramadol are contraindicated through the CYP2D6 prodrug mechanism, and building a safe weight-based multimodal morphine regimen with paired monitoring, constipation prophylaxis, and a naloxone plan. The marks and timing support transparent self-assessment. They are not an official board format or pass standard.
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Target exams
SAQ 1 — Codeine after tonsillectomy
Question 1 — 10 formative marks; suggested time 15 minutes [1]
A previously well four-year-old boy undergoes adenotonsillectomy for obstructive sleep apnoea. The on-call doctor considers prescribing codeine for postoperative analgesia. The child's mother, who is breastfeeding his infant sibling, asks whether she should take codeine herself for a migraine. [1] [2]
- Explain the pharmacological mechanism by which codeine produces analgesia, and why this mechanism makes its effect unpredictable. (3 marks)
- State the current regulatory contraindication of codeine and tramadol in children, and the event that drove it. (4 marks)
- Address the mother's question about codeine in breastfeeding, and outline a safe modern post-tonsillectomy analgesia plan for the child. (3 marks) [2] [3]
Full-credit answer — SAQ 1
Reveal full-credit answer for SAQ 1
1. Mechanism and unpredictability
Codeine is a prodrug with little intrinsic analgesic activity. About 5 to 10 per cent of a dose is O-demethylated by the cytochrome P450 2D6 (CYP2D6) enzyme into morphine, and it is the morphine that provides the analgesia. Because CYP2D6 activity is genetically determined, the conversion varies enormously between individuals: an ultrarapid metaboliser converts codeine to a dangerous excess of morphine, while a poor metaboliser converts almost none and gets no analgesia. The dose written on the prescription therefore does not predict the opioid the child actually receives, which is why codeine is both ineffective in some and lethal in others. Tramadol shares this mechanism, being converted by CYP2D6 to the active O-desmethyltramadol. [2] [3]
2. Regulatory contraindication and the driving event
Codeine is contraindicated in children under 12 years, and contraindicated for the management of postoperative pain in children and adolescents under 18 years after tonsillectomy or adenoidectomy. Tramadol carries the same restrictions. These were issued as a United States Food and Drug Administration boxed warning and as United Kingdom and European Medicines Agency contraindications. They were driven by a series of deaths from respiratory depression in young children, many of them CYP2D6 ultrarapid metabolisers, following tonsillectomy or adenoidectomy for obstructive sleep apnoea. The risk was judged unacceptable given that paracetamol, NSAIDs, and morphine or oxycodone provide better and safer analgesia. [1] [2]
3. Breastfeeding and a safe plan
The mother should not take codeine while breastfeeding. A breastfeeding mother who is a CYP2D6 ultrarapid metaboliser can generate excess morphine and pass it to her infant through breast milk, with documented cases of neonatal opioid toxicity; the same contraindication applies to tramadol. For her migraine I would advise a non-opioid option reviewed by her own prescriber. For the child, a safe modern post-tonsillectomy plan is scheduled paracetamol and ibuprofen with oral morphine or oxycodone as rescue, given with family safety-netting about over-sedation and airway obstruction, and with confirmation at the prescription that codeine and tramadol are absent. Because he has obstructive sleep apnoea, I would monitor him overnight with oximetry and use the smallest effective opioid dose, avoiding any background infusion. [1] [2] [3]
SAQ 2 — A safe postoperative morphine regimen
Question 2 — 10 formative marks; suggested time 15 minutes [9]
A 10-year-old, 32-kilogram girl is admitted overnight after an appendicectomy for a perforated appendix. She is in moderate-to-severe pain despite regular paracetamol and ibuprofen. The team plans to start morphine. She is opioid-naive. [6] [9]
- Outline a multimodal, opioid-sparing analgesia plan, giving the weight-based morphine doses and routes you would use, and justifying the multimodal approach. (4 marks)
- Describe the monitoring you would put in place, including how you would detect opioid-induced respiratory depression early. (3 marks)
- Describe how you would set up patient-controlled analgesia safely, and give your naloxone plan if she becomes over-sedated. (3 marks) [10] [11]
Full-credit answer — SAQ 2
Reveal full-credit answer for SAQ 2
1. Multimodal plan and morphine doses
I would continue scheduled paracetamol and ibuprofen as the non-opioid foundation — multimodal therapy combining non-opioid medicines and non-drug measures produces better pain control at a lower opioid dose, supported by the 2025 JAMA Pediatrics network meta-analysis. I would add morphine for the moderate-to-severe pain. A weight-based regimen for a 32-kilogram child: intravenous morphine 0.1 to 0.2 milligram per kilogram (3 to 6 milligrams) titrated slowly in increments to bring the severe pain under control initially, then either oral morphine 0.2 to 0.5 milligram per kilogram every four hours (about 6 to 16 milligrams per dose) or a morphine infusion at 10 to 40 microgram per kilogram per hour if ongoing intravenous analgesia is needed. I would prescribe a prophylactic stimulant laxative from the first dose, because opioid constipation is near-universal and tolerance does not develop. [6] [8] [9]
2. Monitoring and early detection
I would record a pain score and a sedation score together, before and after every dose, and the respiratory rate and depth, the pupil size, and the oxygen saturation at each assessment. The earliest sign of opioid-induced respiratory depression is a reduction in the depth and then the rate of breathing with rising sedation; oxygen saturation is a late sign and I would not wait for it to fall. Because she is opioid-naive, I would use continuous oximetry while she receives an infusion. A rising sedation score on a stable regimen would prompt dose reduction before apnoea. [9] [10]
3. PCA safety and naloxone plan
For PCA I would use a weight-based morphine bolus of about 20 microgram per kilogram, a lockout of ten to twenty minutes, and no background (basal) infusion, because a background infusion in an opioid-naive child multiplies the risk of respiratory depression from a dose she did not request. I would ensure exclusive ordering, a dedicated line, and paired sedation and oxygen monitoring. If she becomes over-sedated with slow or shallow breathing, I would stimulate her, support the airway and ventilate if needed, and give naloxone 10 microgram per kilogram intravenously, repeated every two to three minutes, titrated to restore her respiratory rate rather than full consciousness to avoid precipitating acute withdrawal and severe pain. Because naloxone has a short half-life, I would observe her for renarcotisation and consider a naloxone infusion if a long-acting opioid or large dose was involved; intranasal naloxone is an option if intravenous access is lost. [10] [11]
References
- [1]Racoosin, Judith A; Roberson, David W; Pacanowski, Mark A; et al New evidence about an old drug — risk with codeine after adenotonsillectomy New England Journal of Medicine, 2013.PMID 23614474
- [2]Tobias, Joseph D; Green, Thomas P; Coté, Charles J; et al Codeine: Time to Say No Pediatrics, 2016.PMID 27647717
- [3]Pratt, Victoria M; Scott, Stuart A; Pirmohamed, Munir; et al Tramadol Therapy and CYP2D6 Genotype Clinical Pharmacology and Therapeutics, 2012.PMID 28520365
- [6]Lynn, Anne; Nespeca, Mary K; Bratton, Sunkyung L; et al Clearance of morphine in postoperative infants during intravenous infusion: the influence of age and surgery Anesthesia and Analgesia, 1998.PMID 9585276
- [8]Olejnik, Lukas; Lima, Joao P; Sadeghirad, Behnam; et al Pharmacologic Management of Acute Pain in Children: A Systematic Review and Network Meta-Analysis JAMA Pediatrics, 2025.PMID 39899301
- [9]Niesters, Monique; Overdyk, Frank; Smith, Thornton; et al Opioid-induced respiratory depression in paediatrics: a review of case reports British Journal of Anaesthesia, 2013.PMID 23248093
- [10]Sharp, Debra; Jaffrani, Aliasgar A PRISMA Systematic Review on the Safety and Efficacy of Patient-Controlled Analgesia (PCA) in Pediatrics Journal of Pediatric Nursing, 2021.PMID 34139608
- [11]Malmros Olsson, Elisabet; Lonnqvist, Per-Arne; Stiller, Cari O; et al Rapid systemic uptake of naloxone after intranasal administration in children Paediatric Anaesthesia, 2021.PMID 33687794