Drug interactions
Fluphenazine + Trihexyphenidyl
Severity: Moderate
Fluphenazine 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 deliberately to relieve fluphenazine-induced extrapyramidal symptoms, but fluphenazine also has anticholinergic activity, so effects such as dry mouth, constipation, urinary retention, blurred vision and confusion can be additive. Anticholinergics may also worsen tardive dyskinesia and cognitive function.
What this interaction means in plain words
Fluphenazine 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.
Fluphenazine belongs to Central Nervous System; Trihexyphenidyl belongs to Central Nervous System.
Why it happens
Additive anticholinergic effects; central muscarinic blockade opposes dopamine-blocker-induced parkinsonism.
What to do
Use trihexyphenidyl only when extrapyramidal symptoms are present and at the lowest effective dose, reviewing the need periodically. Monitor for anticholinergic toxicity, 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 Fluphenazine
- Arsenic trioxide + Fluphenazine Contraindicated
- Dofetilide + Fluphenazine Contraindicated
- Fluphenazine + Ibutilide Contraindicated
- Fluphenazine + Pimozide Contraindicated
- Adagrasib + Fluphenazine Major
- Alfentanil + Fluphenazine Major
Other interactions of Trihexyphenidyl
Frequently asked questions
Can I take Fluphenazine with Trihexyphenidyl?
MediHelp rates the interaction as moderate. Fluphenazine 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 deliberately to relieve fluphenazine-induced extrapyramidal symptoms, but fluphenazine also has anticholinergic activity, so effects such as dry mouth, constipation, urinary retention, blurred vision and confusion can be additive. Anticholinergics may also worsen tardive dyskinesia and cognitive function.
How serious is the interaction between Fluphenazine 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 are present and at the lowest effective dose, reviewing the need periodically. Monitor for anticholinergic toxicity, especially in older patients.
What other medicines interact with Fluphenazine?
MediHelp also lists interactions of Fluphenazine with, for example, Arsenic trioxide, Dofetilide, Ibutilide. The full list is on the Fluphenazine page.
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