Drug interactions
Lorazepam + Promethazine
Severity: Moderate
Lorazepam 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
Combining a sedating antihistamine with a benzodiazepine increases drowsiness, psychomotor impairment and the risk of respiratory depression. The risk is greater in elderly or debilitated patients and with higher doses.
What this interaction means in plain words
Lorazepam 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.
Lorazepam belongs to Central Nervous System; Promethazine belongs to Respiratory.
Why it happens
Additive CNS depression via H1 receptor blockade and GABA-A potentiation.
What to do
Use the lowest effective doses and monitor sedation and respiratory status, especially in the elderly. Advise patients to avoid driving and alcohol.
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
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Other interactions of Lorazepam
Frequently asked questions
Can I take Lorazepam with Promethazine?
MediHelp rates the interaction as moderate. Lorazepam 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. Combining a sedating antihistamine with a benzodiazepine increases drowsiness, psychomotor impairment and the risk of respiratory depression. The risk is greater in elderly or debilitated patients and with higher doses.
How serious is the interaction between Lorazepam 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 sedation and respiratory status, especially in the elderly. Advise patients to avoid driving and alcohol.
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.
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