Weak opioid analgesic Pregnancy: Caution during pregnancy, especially first trimester; possible association with respiratory and cardiac malformations after first-trimester exposure. Regular use may cause fetal drug dependence and neonatal withdrawal. Administration during labour may depress neonatal respiration. Breast-feeding: not recommended (secreted in breast milk; may cause infant respiratory depression) — codeine is contraindicated during breastfeeding.

Codeine phosphate

Codeine is a weak opioid for mild-to-moderate pain (also used for cough or diarrhoea in some settings), frequently combined with paracetamol.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Mild to moderate pain: lowest effective dose, up to 4 times a day at intervals of not less than 6 hours

Route: Oral

Frequency: Up to 4 times a day at intervals of not less than 6 hours

Max: 240 mg codeine daily

Pain: use at the lowest effective dose for the shortest period; duration of treatment limited to 3 days — if no effective relief, seek a physician. Dry or painful cough (adults): 15-30 mg three to four times daily. Diarrhoea (adults): 30 mg three to four times daily (range 15-60 mg). Elderly: dosage should be reduced. Avoid or reduce dose in renal or hepatic impairment. Contraindicated in children under 12 years (risk of opioid toxicity from variable CYP2D6 metabolism) and in CYP2D6 ultra-rapid metabolisers. Contraindicated in all paediatric patients (0-18 years) undergoing tonsillectomy/adenoidectomy for obstructive sleep apnoea. Discuss a treatment-ending strategy before starting (addiction/withdrawal risk).

Dose adjustments

Renal

Avoid or reduce dose in patients with renal impairment

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

DOSAGE AND ADMINISTRATION Important Dosage and Administration Instructions Acetaminophen and codeine phosphate tablets should be prescribed only by healthcare professionals who are knowledgeable about the use of opioids and how to mitigate the associated risks. Use the lowest effective dosage for the shortest duration of time consistent with individual patient treatment goals [see Warnings]. Because the risk of overdose increases as opioid doses increase, reserve titration to higher doses of Acetaminophen and codeine phosphate tablets for patients in whom lower doses are insufficiently effective and in whom the expected benefits of using a higher dose opioid clearly outweigh the substantial …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2025-12-23. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Acute respiratory depression; obstructive airways disease
Hypersensitivity to codeine or other opioid analgesics or to any excipient
Liver disease / severe hepatic dysfunction; acute alcoholism
Raised intracranial pressure or head injury; comatose patients
Conditions where inhibition of peristalsis is to be avoided (risk of paralytic ileus, abdominal distension) or acute diarrhoeal conditions (e.g. ulcerative colitis, antibiotic-associated/pseudomembranous colitis, diarrhoea caused by poisoning); all paediatric patients (0-18 yrs) undergoing tonsillectomy/adenoidectomy for OSA; breastfeeding women; known CYP2D6 ultra-rapid metabolisers

Side effects

Drowsiness, dizziness, headache; nausea, vomiting, constipation, dry mouth
Postural hypotension, facial flushing; tachycardia, palpitations, bradycardia
Respiratory depression (large doses); dyspnoea
Urinary retention, difficulty with micturition; miosis; blurred/double vision
Addiction and tolerance with regular prolonged use; drug withdrawal syndrome

Interactions

Monoamine oxidase inhibitors (MAOIs) — administration of pethidine and possibly other opioid analgesics to patients taking a MAOI has been associated with reactions
CYP2D6 metabolism — deficiency reduces analgesic effect; ultra-rapid/extensive metabolisers at increased risk of opioid toxicity
Other CNS depressants — caution (opioid class effect)

Clinical monograph

How it works

Codeine is a prodrug converted by CYP2D6 to morphine, which acts on opioid receptors; analgesic effect therefore varies with metaboliser status.

Prescribing in practice

Effect varies with CYP2D6 status — ultra-rapid metabolisers risk toxicity and poor metabolisers gain little benefit.
MHRA restrictions: avoid in children under 12, after tonsillectomy/adenoidectomy for obstructive sleep apnoea in under-18s, and in breastfeeding.
It is a controlled drug — counsel on constipation, dependence and additive sedation/respiratory depression with other CNS depressants.

Monitoring

Review pain relief, bowel habit and signs of dependence; reassess the ongoing need.

Counselling the patient

It commonly causes constipation — a laxative may be needed.
Do not combine it with alcohol or other sedatives.
Take it only as prescribed; it can be habit-forming.

Evidence & guidelines

A step on the analgesic ladder for mild-to-moderate pain, with MHRA safety restrictions in children and breastfeeding.

Reference: MHRA Drug Safety Update; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Dihydrocodeine · Weak opioid analgesic

Pathways