Drug interactions
Diazepam intranasal + Promethazine
Severity: Moderate
Diazepam intranasal 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 adds to the CNS-depressant effects of diazepam, increasing the risk of excessive sedation, dizziness, impaired coordination and respiratory depression. This matters in the elderly and in patients with lung disease or taking other sedatives.
What this interaction means in plain words
Diazepam intranasal 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.
Why it happens
Additive CNS depression through H1 receptor blockade and GABA-A receptor potentiation.
What to do
Monitor level of consciousness and respiratory status, use the lowest effective doses, and advise against driving or operating machinery.
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
Frequently asked questions
Can I take Diazepam intranasal with Promethazine?
MediHelp rates the interaction as moderate. Diazepam intranasal 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 adds to the CNS-depressant effects of diazepam, increasing the risk of excessive sedation, dizziness, impaired coordination and respiratory depression. This matters in the elderly and in patients with lung disease or taking other sedatives.
How serious is the interaction between Diazepam intranasal 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: Monitor level of consciousness and respiratory status, use the lowest effective doses, and advise against driving or operating machinery.
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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