Drug interactions
Tiotropium + Trihexyphenidyl
Severity: Moderate
Tiotropium 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 a strong antimuscarinic, and combining it with tiotropium increases the risk of anticholinergic effects. These include dry mouth, constipation, urinary retention, blurred vision, tachycardia and confusion, particularly in older adults.
What this interaction means in plain words
Tiotropium 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.
Tiotropium belongs to Respiratory; Trihexyphenidyl belongs to Central Nervous System.
Why it happens
Additive antimuscarinic pharmacodynamic effects.
What to do
Monitor for anticholinergic toxicity, including cognitive changes and urinary retention. Use the lowest effective trihexyphenidyl dose and avoid in narrow-angle glaucoma.
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 Tiotropium
Other interactions of Trihexyphenidyl
Frequently asked questions
Can I take Tiotropium with Trihexyphenidyl?
MediHelp rates the interaction as moderate. Tiotropium 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 a strong antimuscarinic, and combining it with tiotropium increases the risk of anticholinergic effects. These include dry mouth, constipation, urinary retention, blurred vision, tachycardia and confusion, particularly in older adults.
How serious is the interaction between Tiotropium 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, including cognitive changes and urinary retention. Use the lowest effective trihexyphenidyl dose and avoid in narrow-angle glaucoma.
What other medicines interact with Tiotropium?
MediHelp also lists interactions of Tiotropium with, for example, Glycopyrrolate inhaled, Indacaterol-glycopyrronium, Revefenacin. The full list is on the Tiotropium page.
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