CautionCodeine phosphate
Codeine
Opioid prodrug (CYP2D6 → morphine)
Contraindicated in breastfeeding — MHRA and FDA warning.
Oral
First-line for
- Short-course analgesia in non-breastfeeding adults (with paracetamol)
Mechanism
CYP2D6-mediated O-demethylation to morphine → μ-opioid agonism; extent varies with genotype.
"Codeine = Categorically avoid in breastfeeding"
- Ultra-rapid metabolisers → neonatal fatality
- Use paracetamol ± ibuprofen ± dihydrocodeine instead
- Not licensed <12 y or post-adenotonsillectomy
Dosing
- Adult
- 30–60 mg 4-hourly PRN, max 240 mg/day
Contraindications
- AbsoluteBreastfeeding (MHRA 2013)
- AbsoluteChildren <12 years
- AbsoluteKnown CYP2D6 ultra-rapid metaboliser
- AbsolutePost-tonsillectomy/adenoidectomy in children
Side effects
- Constipation (universal)
- Sedation, nausea
- Dependence with prolonged use
- Respiratory depression
Fetal & maternal notes
- • Not first-line in pregnancy — occasional short doses acceptable before term; watch neonatal withdrawal if chronic near delivery
Key interactions
CYP2D6 inhibitors (paroxetine, fluoxetine)
Caution↓ conversion — inadequate analgesia
Other CNS depressants
AvoidRespiratory depression
Clinical pearls
- 💡 Prescribe laxative alongside if course >3 days
- 💡 For lactating women: paracetamol + ibuprofen ± dihydrocodeine short course
Content last reviewed: REPLACE_ME (e.g. 2026-07)
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