First-Generation Antihistamine — Burns Pruritus / Sedation Pregnancy: Use with caution — avoid in third trimester (neonatal depression and irritability reported)

Promethazine

Brand names: Phenergan

Adult dose

Dose: 25–50 mg oral or IM; pruritus: 25 mg at night or 10–25 mg three times daily

Route: Oral / IM

Frequency: Once to three times daily

Max: 100 mg/day

Used in burns for: post-burn itch (neuropathic and histamine-mediated), procedural anxiolysis, and antiemetic. Sedating antihistamine — useful for night-time itch disrupting sleep. IM injection painful — use deep IM into large muscle. IV use not recommended (risk of gangrene with inadvertent intra-arterial injection).

Paediatric dose

Dose: 0.5 mg/kg

Route: Oral

Frequency: At night or twice daily

Max: 25 mg/dose

Children ≥2 years only — NEVER use under 2 years (risk of fatal respiratory depression). 0.5 mg/kg at night for pruritus. Antiemetic: 0.25 mg/kg every 4–6 hours.

Dose adjustments

Renal

No specific adjustment — use with caution; increased sedation risk.

Hepatic

Caution in hepatic impairment — reduced metabolism. Use lowest effective dose.

Paediatric weight-based calculator

Patient weight (kg)

Children ≥2 years only — NEVER use under 2 years (risk of fatal respiratory depression). 0.5 mg/kg at night for pruritus. Antiemetic: 0.25 mg/kg every 4–6 hours.

Clinical pearls

MHRA black box: NEVER use in children under 2 years — risk of fatal respiratory depression. This is an absolute contraindication.
IV route absolutely contraindicated — inadvertent intra-arterial injection causes severe tissue necrosis and gangrene (peripheral vasoconstriction and arterial spasm)
Post-burn itch often has both histaminergic and neuropathic components — combine promethazine (histaminergic) with gabapentin (neuropathic) for comprehensive anti-pruritic therapy

Contraindications

Children under 2 years (risk of fatal respiratory depression)
CNS depression
Phaeochromocytoma
Epilepsy (lowers seizure threshold)
IV administration

Side effects

Sedation (significant — useful therapeutically)
Antimuscarinic effects (dry mouth, urinary retention, blurred vision, constipation)
Extrapyramidal reactions (rare)
Paradoxical excitation (especially children)
Respiratory depression (children <2 years — contraindicated)

Interactions

CNS depressants/opioids (marked additive sedation)
MAOIs (contraindicated)
Anticholinergic drugs (additive antimuscarinic effects)
Alcohol (severe CNS depression)

Monitoring

Sedation level
Signs of extrapyramidal reactions
Antimuscarinic side effects (urinary retention in elderly men)

Reference: BNFc; BNF 90; MHRA Promethazine Safety Update (Under-2s); BBA Burns Pruritus Management Guidelines; BNFc. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators