Drug interactions
Promethazine + Quazepam
Severity: Moderate
Promethazine and Quazepam: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Quazepam is a benzodiazepine hypnotic with long-acting active metabolites. Adding promethazine increases sedation, psychomotor impairment and the risk of respiratory depression and next-day impairment.
What this interaction means in plain words
Promethazine and Quazepam can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Additive CNS depression via GABA-A potentiation and H1 receptor blockade.
What to do
Use the lowest effective doses and avoid alcohol and other sedatives. Counsel about next-day impairment, and take extra care in older adults.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Promethazine and Quazepam, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Promethazine
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Frequently asked questions
Can I take Promethazine with Quazepam?
MediHelp rates the interaction as moderate. Promethazine and Quazepam can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Quazepam is a benzodiazepine hypnotic with long-acting active metabolites. Adding promethazine increases sedation, psychomotor impairment and the risk of respiratory depression and next-day impairment.
How serious is the interaction between Promethazine and Quazepam?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use the lowest effective doses and avoid alcohol and other sedatives. Counsel about next-day impairment, and take extra care in older adults.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Promethazine page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
