About promethazine hcl
First-generation antihistamine; phenothiazine
Used for
- Allergy symptoms and allergic reactions
- Nausea and vomiting, including motion sickness
- Sedation before or after procedures
Usual adult dose
Usually 12.5–25 mg by deep intramuscular injection; dose and timing depend on the use. Intravenous use is generally avoided.
Usual dose in children
Not recommended for children under 2 years. For older children, dosing is weight-based and requires clinician supervision.
Common side effects
- Drowsiness, dizziness, confusion
- Dry mouth, blurred vision, constipation
- Low blood pressure
- Injection-site injury or tissue damage
Important warnings
- Can cause severe breathing suppression; contraindicated under age 2.
- Injection can cause severe tissue injury; deep intramuscular administration is preferred.
- Avoid injecting into an artery or under the skin.
- May impair alertness; alcohol and sedatives increase this effect.
Pregnancy
Use only when clearly needed; safety evidence is limited. Near delivery, use may affect the newborn.
Breastfeeding
May cause infant drowsiness or irritability and can reduce milk supply; use requires clinical assessment.
Interactions
- Alcohol, opioids, and sedatives increase drowsiness and breathing suppression.
- Anticholinergic medicines can worsen dry mouth, constipation, and blurred vision.
- Medicines that prolong the QT interval may increase abnormal heart rhythm risk.
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 It may be incomplete or out of date.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.