About promethazine hcl
First-generation antihistamine and phenothiazine
Used for
- Allergy symptoms, including sneezing, itching, and runny nose
- Motion sickness prevention and treatment
- Short-term treatment of nausea and vomiting
- Sedation before or after procedures, when prescribed
Usual adult dose
Allergies: 25 mg at bedtime or 12.5 mg before meals and bedtime. Motion sickness: 25 mg before travel, then as needed.
Usual dose in children
Not for children under 2 years. For older children, dosing is weight-based and must be prescribed; it varies by use.
Common side effects
- Sleepiness and dizziness
- Dry mouth, blurred vision, or constipation
- Confusion or impaired coordination
- Low blood pressure
Important warnings
- Can dangerously slow breathing; contraindicated under age 2.
- Avoid alcohol and activities requiring alertness until effects are known.
- Use caution with breathing problems, glaucoma, urinary retention, or older age.
- Seek urgent care for severe breathing difficulty, fainting, or unusual movements.
Pregnancy
Use only when clearly needed after discussion with a healthcare professional; risks and benefits depend on timing and circumstances.
Breastfeeding
May cause infant sleepiness or irritability and may reduce milk supply; discuss use with a healthcare professional.
Interactions
- Alcohol, opioids, and sedatives increase sleepiness and breathing risks.
- Other anticholinergic medicines can worsen dry mouth, constipation, or urinary problems.
- Monoamine oxidase inhibitors may intensify effects.
- May interfere with some laboratory pregnancy tests.
AI-generated from general medical knowledge, not from this product's official leaflet. It may be incomplete or out of date. Not medical advice — ask a pharmacist or doctor before making any decision.