⚠️ Safety notes: - Caution in elderly or those with renal, hepatic, or cardiac impairment → accumulation can cause sedation, delirium, or coma. - Codeine is a pro-drug metabolised to morphine by CYP2D6. - 240 mg codeine ≈ 30 mg morphine.

📖 About

Always check the BNF link here.

💊 Weak opioid analgesic (step 2 of WHO analgesic ladder).
🧠 Can cause confusion and delirium in elderly patients.
⚠️ Genetic variation in CYP2D6 metabolism → some patients are ultra-rapid metabolisers (risk of toxicity) while others are poor metabolisers (poor efficacy).

⚡ Mechanism of Action

Acts as an agonist at opioid receptors (μ-opioid receptor).
Most of its analgesic effect occurs after conversion to morphine via hepatic metabolism.
Also has central anti-tussive and peripheral anti-diarrhoeal effects.

🩺 Indications & Dosing – Codeine (verify with BNF/datasheet)

Indication	Details
🤕 Pain Relief	Adults: 30–60 mg PO/IM every 4 h PRN (max 240 mg/24 h) Elderly/renal impairment: 15 mg PO/IM every 4 h PRN 💊 Often used in combination (e.g. Co-codamol = codeine + paracetamol) ⚠️ Not for long-term use (risk: dependence & constipation)
💨 Antitussive (cough suppressant)	Rarely used now due to risk profile (historical use at lower doses)
💩 Anti-diarrhoeal	Rarely used for this purpose in modern practice

🔄 Interactions

⚠️ Avoid with MAOIs (risk of serotonin syndrome, hypertensive crisis).
⬆️ Sedation risk when combined with alcohol, benzodiazepines, or other CNS depressants.
Metabolism altered by CYP2D6 inhibitors (e.g. fluoxetine, paroxetine) and inducers.

⚠️ Cautions

👵 Elderly – high risk of delirium, sedation, constipation.
💧 Renal impairment (accumulation of active metabolites).
🫀 Heart failure, hypotension.
🫁 Asthma or COPD (respiratory depression risk).
🤰 Pregnancy/breastfeeding – avoid (toxic morphine levels may pass to neonate, especially if mother is ultra-rapid metaboliser).

🚫 Contraindications

Acute respiratory depression.
Paralytic ileus.
Known hypersensitivity to opioids.
Children post-tonsillectomy/adenoidectomy (risk of fatal respiratory depression in ultra-rapid metabolisers).

💥 Side Effects

🫁 Respiratory depression, coma (reverse with naloxone if severe).
🧠 Sedation, dizziness, delirium, hallucinations.
👀 Miosis (pinpoint pupils).
💩 Constipation (always consider laxative co-prescription).
🤢 Nausea, vomiting.
🦠 Dependence, tolerance, and withdrawal symptoms with chronic use.
Rare: hypersensitivity reactions, pancreatitis, urinary retention.

📑 References

BNF: Codeine Phosphate
MHRA Guidance on Codeine Use in Children (2013)

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Codeine