Drug interactions
Olanzapine / samidorphan + Promethazine
Severity: Moderate
Olanzapine / samidorphan 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
Both olanzapine and promethazine have anticholinergic and sedating properties. Together they may increase drowsiness, constipation, urinary retention and in severe cases gastrointestinal hypomotility or ileus.
What this interaction means in plain words
Olanzapine / samidorphan 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 antimuscarinic and CNS depressant effects (H1 and muscarinic blockade).
What to do
Monitor for constipation, abdominal distension, urinary retention and excessive sedation. Use a bowel regimen if needed and consider a non-anticholinergic antiemetic or antihistamine.
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
Frequently asked questions
Can I take Olanzapine / samidorphan with Promethazine?
MediHelp rates the interaction as moderate. Olanzapine / samidorphan 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. Both olanzapine and promethazine have anticholinergic and sedating properties. Together they may increase drowsiness, constipation, urinary retention and in severe cases gastrointestinal hypomotility or ileus.
How serious is the interaction between Olanzapine / samidorphan 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 for constipation, abdominal distension, urinary retention and excessive sedation. Use a bowel regimen if needed and consider a non-anticholinergic antiemetic or antihistamine.
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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