Drug reference

Promethazine hydrochloride

Antihistamine · Antihistamine, Antiemetic, Sedative

Also known as Promethazine teoclate

AntihistamineAntihistamine, Antiemetic, Sedative

CDSCO approved

EXCRETION

—

not curated

INTERACTIONS

—

none in our sources

PREGNANCY

Most manufacturers advise avoiding use during pregnancy; however, there is no evidence of teratogenicity. Use in the latter part of the third trimester may cause adverse effects in neonates such as irritability, paradoxical excitability, and tremor.

FDA category + note

Mechanism

Promethazine is an older, sedating antihistamine that likely acts as an H1 receptor antagonist, reducing histamine-mediated allergic symptoms like rhinorrhoea and sneezing. Its sedating effects are due to its ability to penetrate the blood-brain barrier.

Indications

Symptomatic relief of allergy such as hay fever and urticariaInsomnia associated with urticaria and pruritusEmergency treatment of anaphylactic reactions (as an adjunct to adrenaline/epinephrine)Sedation (short-term use)NauseaVomitingVertigoLabyrinthine disordersMotion sickness

Dosing

Adult: Symptomatic relief of allergy / Insomnia: PO 10–20 mg 2–3 times a day. Emergency treatment of anaphylactic reactions: Deep IM 25–50 mg; Slow IV 25–50 mg (as a solution containing 2.5 mg/mL in water for injections). Sedation (short-term use): PO 25–50 mg; Deep IM 25–50 mg.…
Pediatric: Symptomatic relief of allergy / Insomnia: Child 2–4 years: PO 5 mg twice daily, alternatively 5–15 mg once daily at night. Child 5–9 years: PO 5–10 mg twice daily, alternatively 10–25 mg once daily at night. Child 10–17 years: PO 10–20 mg 2–3 times a day, alternatively 25 mg once daily at night, increased if necessary to 25 mg twice daily. Sedation (short-term use): Child 2–4 years: PO 15–20 mg.…
Geriatric: Use of first-generation antihistamines in elderly patients is potentially inappropriate (STOPP criteria).
Max dose: Emergency treatment of anaphylactic reactions: 100 mg per dose (IM); 100 mg per course (IV).

Contraindications

Elderly patients (potentially inappropriate per STOPP criteria)
Children under 6 years (for over-the-counter cough and cold medicines containing promethazine)
Epilepsy
Prostatic hypertrophy (in adults)
Pyloroduodenal obstruction
Severe coronary artery disease
Susceptibility to angle-closure glaucoma
Urinary retention
Latter part of the third trimester of pregnancy (due to potential adverse effects in neonates)

Side effects

Common

SedationDrowsiness (may diminish after a few days)Paradoxical stimulation (rarely, especially with high doses or in children and the elderly)Irritability (in neonates if used in late third trimester of pregnancy)Paradoxical excitability (in neonates if used in late third trimester of pregnancy)Tremor (in neonates if used in late third trimester of pregnancy)

Serious