Weak opioid analgesic
Codeine phosphate
Adult dose
Dose: 30–60mg every 4h PO/IM (max 240mg/24h). Diarrhoea: 30mg TDS-QDS
Route: PO/IM
Frequency: 4-hourly
Paediatric dose
Route: PO
Frequency: 4–6h
NOT for children <12. ≥12 only after surgery if other analgesia inadequate, AND not in patients of any age <18 with obstructive sleep apnoea / post-tonsillectomy
Clinical pearls
- Pro-drug — analgesia depends on CYP2D6 metabolism to morphine; effect highly variable
- MHRA: avoid in <18 post-tonsillectomy/adenoidectomy
Contraindications
- Children <12
- Breastfeeding
- Known CYP2D6 ultra-rapid metabolisers
- Acute respiratory depression
- Paralytic ileus
Side effects
- Constipation
- Drowsiness
- Respiratory depression
- Nausea
- Dependence
- Tolerance
Interactions
- CNS depressants
- MAOIs
- CYP2D6 inhibitors (fluoxetine, paroxetine — reduce conversion to morphine)
Reference: BNFc; BNF; MHRA Drug Safety Update; https://bnf.nice.org.uk/drugs/codeine-phosphate/. Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.
Calculators
- Morphine Milligram Equivalents (MME) Calculator · Pain / Opioids
- Opioid Conversion / Equianalgesic Guide · Pain Management
- Numeric Rating Scale (NRS) Pain Assessment and Management · Pain Management
- Finnegan Neonatal Abstinence Scoring Tool (FNAST) · Neonatal Abstinence Syndrome
- Modified Finnegan Neonatal Abstinence Score (NAS) · Neonatal
- Withdrawal Assessment Tool (WAT-1) for Paediatric Iatrogenic Withdrawal · Critical Care
Pathways
- New-Onset Atrial Fibrillation · ESC 2020 AF Guidelines; NICE NG196
- Hypertensive Emergency · ESC/ESH 2018 Hypertension Guidelines; NICE NG136
- Bradycardia Management · Resuscitation Council UK ABCDE; ESC 2021 Pacing Guidelines
- Ventricular Tachycardia / Fibrillation · Resuscitation Council UK ACLS; ESC 2022 Ventricular Arrhythmia Guidelines
- Syncope Assessment · ESC 2018 Syncope Guidelines; NICE NG109
- Acute Chest Pain · NICE CG95; ESC 2023 ACS Guidelines