Drug interactions
Olanzapine / samidorphan + Trihexyphenidyl
Severity: Moderate
Olanzapine / samidorphan and Trihexyphenidyl: 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
Olanzapine has antimuscarinic activity, and adding trihexyphenidyl raises the risk of severe gastrointestinal hypomotility, including constipation and ileus. Urinary retention, sedation and confusion may also be increased.
What this interaction means in plain words
Olanzapine / samidorphan and Trihexyphenidyl 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 muscarinic receptor antagonism reducing gastrointestinal and urinary tract motility.
What to do
Monitor bowel function and urinary symptoms, and use a bowel regimen or lower the anticholinergic dose if constipation develops.
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 Trihexyphenidyl
Frequently asked questions
Can I take Olanzapine / samidorphan with Trihexyphenidyl?
MediHelp rates the interaction as moderate. Olanzapine / samidorphan and Trihexyphenidyl 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. Olanzapine has antimuscarinic activity, and adding trihexyphenidyl raises the risk of severe gastrointestinal hypomotility, including constipation and ileus. Urinary retention, sedation and confusion may also be increased.
How serious is the interaction between Olanzapine / samidorphan and Trihexyphenidyl?
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 bowel function and urinary symptoms, and use a bowel regimen or lower the anticholinergic dose if constipation develops.
What other medicines interact with Trihexyphenidyl?
MediHelp also lists interactions of Trihexyphenidyl with, for example, Orphenadrin, Oxybutynin, Scopolamine. The full list is on the Trihexyphenidyl page.
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