Drug interactions
Clonazepam + Promethazine
Severity: Moderate
Clonazepam and Promethazine: 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
Promethazine and clonazepam produce additive sedation and psychomotor impairment. Excessive CNS and respiratory depression can occur, especially in elderly patients or with higher doses.
What this interaction means in plain words
Clonazepam and Promethazine 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.
Clonazepam belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Additive CNS depression via H1 antagonism and GABA-A potentiation.
What to do
Use the lowest effective doses and monitor for oversedation and respiratory depression. Advise avoiding alcohol and driving.
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?
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Other interactions of Promethazine
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
Other interactions of Clonazepam
- Calcium / magnesium / potassium / sodium oxybates + Clonazepam Contraindicated
- Clonazepam + Sodium oxybate Contraindicated
- Alfentanil + Clonazepam Major
- Alprazolam + Clonazepam Major
- Amobarbital + Clonazepam Major
- Belladonna and opium + Clonazepam Major
Frequently asked questions
Can I take Clonazepam with Promethazine?
MediHelp rates the interaction as moderate. Clonazepam and Promethazine 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. Promethazine and clonazepam produce additive sedation and psychomotor impairment. Excessive CNS and respiratory depression can occur, especially in elderly patients or with higher doses.
How serious is the interaction between Clonazepam and Promethazine?
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 monitor for oversedation and respiratory depression. Advise avoiding alcohol and driving.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Cabergoline, Dopamine, Ibutilide. The full list is on the Promethazine page.
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