Promethazine: Uses, Interactions and Safety
Uses
Promethazine is a first-generation antihistamine with sedative and antiemetic effects. Oral indications vary by country. The UK Phenergan tablet label includes allergic symptoms, nausea and vomiting, and short-term adult insomnia. For anaphylaxis it is only an adjunct to standard emergency treatment.
Administration
This page concerns oral tablets. Injectable and rectal products require their own instructions. Do not use for longer than seven days without medical advice. Children should not be given promethazine simply to make them sleep. Check the exact local label before any pediatric use.
Safety
The UK tablet is contraindicated below six years of age because of potentially fatal respiratory depression and psychiatric or neurological effects. A US oral label uses a below-two-years contraindication and strong precautions in older children; that age threshold must not replace the UK restriction. Coma or existing central nervous system depression also precludes use. Breathing disorders, glaucoma, urinary obstruction and seizure history require particular attention.
Interactions
Alcohol, opioids, benzodiazepines and other sedatives can amplify impaired alertness and breathing suppression. Antimuscarinic medicines increase constipation and urinary retention. QT-prolonging medicines require careful review because serious heart rhythm effects can be additive. The UK label says to avoid MAO inhibitors during treatment and for the preceding fourteen days. Amitriptyline exposure may rise and needs monitoring.
Pregnancy and breastfeeding
The UK label does not recommend pregnancy use unless benefits outweigh risks. Exposure to high doses late in pregnancy has been associated with prolonged neurological effects in infants. Breastfeeding use is not recommended because promethazine enters milk.
Adverse effects
Sleepiness is very common. Dry mouth, blurred vision, constipation and dizziness may occur. Seek urgent care for slow breathing, fainting, severe allergy, seizures or fever with muscle stiffness and confusion.
Sources
- Phenergan 25 mg Tablets – Summary of Product Characteristics (19/06/2024)
- Turkish Ministry of Education: Premedication Medicines (Ankara, 2010)
- Promethazine hydrochloride tablets – US prescribing information (DailyMed updated 2026-05-22)
- ZYVOX (linezolid) – US prescribing information (Revised 6/2026; LAB-0139-46.0)
The linked Turkish profile contains the medicine record and its documented interaction list.