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Opioid Analgesic (Weak) Pregnancy: Avoid in third trimester — neonatal withdrawal and respiratory depression

Codeine Phosphate

Brand names: Codeine Linctus, Codipar (combination)

Adult dose

Dose: 15-60 mg every 4-6 hours
Route: Oral / IM
Frequency: Every 4-6 hours as required
Max: 240 mg/day
For acute pain only; not recommended for chronic non-cancer pain in elderly

Paediatric dose

Dose: Seek specialist opinion N/A/kg
Route: Oral
Frequency: Seek specialist opinion
Max: Seek specialist opinion
Contraindicated under 12 years for any indication; contraindicated under 18 after tonsillectomy/adenoidectomy (MHRA 2015)

Dose adjustments

Renal

Reduce dose and frequency in renal impairment — active metabolite (morphine) accumulates

Hepatic

Avoid in severe hepatic impairment

Paediatric weight-based calculator

Contraindicated under 12 years for any indication; contraindicated under 18 after tonsillectomy/adenoidectomy (MHRA 2015)

Clinical pearls

  • Codeine is a prodrug — converted to morphine by CYP2D6; approximately 7% of Caucasians are poor metabolisers and get little analgesia; ultra-rapid metabolisers risk opioid toxicity
  • MHRA 2013: Codeine contraindicated in children under 12 and in all patients for post-tonsillectomy pain under 18 following paediatric deaths from respiratory depression
  • STOPP criteria: avoid regular (daily) codeine for chronic non-cancer pain in elderly — use non-opioid alternatives first
  • Highly constipating — always co-prescribe laxative (stimulant, e.g. senna) in elderly to prevent faecal impaction
  • Consider paracetamol alone first before adding codeine — equivalent efficacy data for mild-moderate pain

Contraindications

  • Known ultra-rapid CYP2D6 metaboliser status
  • Respiratory depression
  • Paralytic ileus
  • Children under 12 years (MHRA 2013)

Side effects

  • Constipation (very common)
  • Nausea and vomiting
  • Sedation and confusion (elderly)
  • Respiratory depression (ultra-rapid metabolisers)
  • Dependence

Interactions

  • MAOIs (avoid)
  • CNS depressants (additive)
  • CYP2D6 inhibitors — fluoxetine, paroxetine (reduce conversion to morphine, reduce efficacy)

Monitoring

  • Pain scores
  • Respiratory rate
  • Bowel function
  • Sedation

Reference: BNFc; BNF 90; MHRA Drug Safety Update 2013 (codeine in children); AGS Beers Criteria 2023; STOPP/START v3. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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