Drug interactions
Thioridazine + Trihexyphenidyl
Severity: Moderate
Thioridazine 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
Both drugs have anticholinergic activity, so combined use can cause dry mouth, constipation, urinary retention, blurred vision, confusion and heat intolerance. Trihexyphenidyl is often given to treat phenothiazine-induced parkinsonism, which makes the combination common in practice.
What this interaction means in plain words
Thioridazine 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.
Thioridazine belongs to Central Nervous System; Trihexyphenidyl belongs to Central Nervous System.
Why it happens
Additive antimuscarinic effects.
What to do
Monitor for anticholinergic toxicity, especially in older patients, and use the lowest effective trihexyphenidyl dose.
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 Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Other interactions of Trihexyphenidyl
Frequently asked questions
Can I take Thioridazine with Trihexyphenidyl?
MediHelp rates the interaction as moderate. Thioridazine 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. Both drugs have anticholinergic activity, so combined use can cause dry mouth, constipation, urinary retention, blurred vision, confusion and heat intolerance. Trihexyphenidyl is often given to treat phenothiazine-induced parkinsonism, which makes the combination common in practice.
How serious is the interaction between Thioridazine 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 for anticholinergic toxicity, especially in older patients, and use the lowest effective trihexyphenidyl dose.
What other medicines interact with Thioridazine?
MediHelp also lists interactions of Thioridazine with, for example, Abiraterone, Adagrasib, Amiodarone. The full list is on the Thioridazine page.
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