What it's for (Indications)
- Relief of nausea and vomiting associated with various conditions, including motion sickness and post-operative states.
- May also be used for symptomatic relief of allergic conditions, although its sedative properties often lead to it being reserved for cases where sedation is beneficial.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | Adults: For nausea and vomiting, typically 12.5 mg to 25 mg taken orally every 4 to 6 hours as needed, or 25 mg at night. For motion sickness, 25 mg taken orally 30-60 minutes before travel, then 25 mg 8-12 hours later if necessary. Maximum daily dose generally should not exceed 100 mg. For allergic conditions, 12.5 mg to 25 mg orally at night, or 6.25 mg to 12.5 mg three times daily. Pediatric Patients (2 years and older): Use with extreme caution due to the risk of respiratory depression. Dosage should be carefully determined by a healthcare professional, typically 0.5 mg/kg per dose. Not for use in children under 2 years of age. Local Pakistani clinical practice may follow similar guidelines but should always prioritize patient safety and adhere to the contraindication in children <2 years. |
Safety & Warnings
Common Side Effects
- Common: Drowsiness/sedation, dizziness, dry mouth, blurred vision, urinary retention, constipation, headache.
- Less common/Serious: Paradoxical excitation (especially in children), respiratory depression (potentially fatal, particularly in children <2 years), extrapyramidal symptoms (e.
- g.
- , dystonia, akathisia), neuroleptic malignant syndrome (NMS), orthostatic hypotension, photosensitivity, agranulocytosis, leukopenia, thrombocytopenia, jaundice, seizures, prolonged QTc interval (rare).
Serious Warnings
- Black Box Warning: Promethazine is contraindicated for use in pediatric patients less than 2 years of age because of the potential for fatal respiratory depression. Postmarketing cases of respiratory depression, including fatalities, have been reported with use in pediatric patients less than 2 years of age. Caution should be exercised when administering promethazine to pediatric patients 2 years of age and older.
- Risk of severe respiratory depression, potentially fatal, especially in pediatric patients less than 2 years of age and in those with compromised respiratory function.
- Use with extreme caution in children aged 2 years and older, and avoid in those with signs of respiratory depression.
- May impair mental and/or physical abilities required for driving or operating machinery.
- Concomitant use with other CNS depressants (e.
- g.
- , alcohol, opioids, anxiolytics) can potentiate sedation and respiratory depression.
- Caution in patients with cardiovascular disease, narrow-angle glaucoma, prostatic hypertrophy, urinary retention, asthma, COPD, sleep apnea, seizure disorders, or hepatic impairment.
- May cause photosensitivity.
- Discontinue if signs of NMS or extrapyramidal symptoms develop.
- Avoid abrupt discontinuation after prolonged use.
How it Works (Mechanism of Action)
Promethazine, a phenothiazine derivative, acts primarily as a potent H1-receptor antagonist (inverse agonist), blocking the effects of histamine. It also possesses significant anticholinergic, moderate sedative, and some antidopaminergic and alpha-adrenergic blocking activities. These combined actions contribute to its antiemetic effects (via inhibition of the chemoreceptor trigger zone and vestibular pathways) and its sedative properties. Theoclate (8-chlorotheophyllinate) is a salt component often used to enhance the antiemetic properties and may slightly mitigate the pronounced sedation of promethazine hydrochloride, although sedation remains a prominent side effect.
Commercial Brands (Alternatives)
No other brands found for this formula.