Drug interactions
Perphenazine + Trihexyphenidyl
Severity: Moderate
Perphenazine 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
Trihexyphenidyl is often given to treat perphenazine-induced extrapyramidal symptoms, but both have anticholinergic activity. Together they can cause dry mouth, constipation, urinary retention, confusion and heat intolerance, particularly in older adults.
What this interaction means in plain words
Perphenazine 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.
Perphenazine belongs to Central Nervous System; Trihexyphenidyl belongs to Central Nervous System.
Why it happens
Additive antimuscarinic effects.
What to do
Use trihexyphenidyl only when extrapyramidal symptoms occur and reassess regularly. Monitor for cognitive impairment, urinary retention and constipation, especially in older patients.
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 Perphenazine
- Ibutilide + Perphenazine Contraindicated
- Perphenazine + Pimozide Contraindicated
- Perphenazine + Thioridazine Contraindicated
- Adagrasib + Perphenazine Major
- Alfentanil + Perphenazine Major
- Amiodarone + Perphenazine Major
Other interactions of Trihexyphenidyl
Frequently asked questions
Can I take Perphenazine with Trihexyphenidyl?
MediHelp rates the interaction as moderate. Perphenazine 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. Trihexyphenidyl is often given to treat perphenazine-induced extrapyramidal symptoms, but both have anticholinergic activity. Together they can cause dry mouth, constipation, urinary retention, confusion and heat intolerance, particularly in older adults.
How serious is the interaction between Perphenazine 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: Use trihexyphenidyl only when extrapyramidal symptoms occur and reassess regularly. Monitor for cognitive impairment, urinary retention and constipation, especially in older patients.
What other medicines interact with Perphenazine?
MediHelp also lists interactions of Perphenazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Perphenazine page.
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