Promethazine Injectable: Dosing and Precautions

Therapeutic action

Sedating H1 antihistamine.

Indications

Agitation or aggressive behaviour in patients with acute or chronic psychosis, in combination with haloperidol.

Forms and strengths, route of administration

• 50 mg in 2 ml ampoule (25 mg/ml) for deep IM injection.
• Never administer by SC injection.

Dose and duration

• Adult: 25 mg, to be repeated after 30 minutes if necessary.
• If no response 30 minutes after the second dose, administer 50 mg.
• Maximum total dose 100 mg.

Contra-indications, adverse effects, precautions

• Administer with caution and monitor use in older patients.
• Administer with caution in patients with prostate disorders, closed-angle glaucoma, epilepsy, orthostatic hypotension, severe renal or hepatic impairment, or those taking CNS depressants or drugs with anticholinergic effects.
• May cause drowsiness, dizziness, headache, confusional state, hypotension, photosensitivity, anticholinergic effects, tissue damage including necrosis, and rarely seizures, extrapyramidal syndrome, neuroleptic malignant syndrome, and allergic reactions.
• Pregnancy and breast-feeding: avoid.
• Promethazine by IV route should only be used in intensive care at a maximum concentration of 1 mg/ml by infusion over 20 minutes using a central catheter or a large-bore peripheral catheter.
• Promethazine is not included in the WHO list of essential medicines.