Drug interactions
Tolterodine + Trihexyphenidyl
Severity: Moderate
Tolterodine 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 are antimuscarinic, so combined use increases the risk of dry mouth, constipation, urinary retention, blurred vision, tachycardia, confusion, and delirium. Older patients are especially vulnerable to cognitive effects and heat intolerance.
What this interaction means in plain words
Tolterodine 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.
Tolterodine belongs to Genitourinary; Trihexyphenidyl belongs to Central Nervous System.
Why it happens
Additive pharmacodynamic blockade of muscarinic receptors.
What to do
Avoid the combination in older or cognitively impaired patients where possible. If it is used, monitor for confusion, urinary retention, and constipation and use the lowest effective doses.
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 Tolterodine
Other interactions of Trihexyphenidyl
Frequently asked questions
Can I take Tolterodine with Trihexyphenidyl?
MediHelp rates the interaction as moderate. Tolterodine 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 are antimuscarinic, so combined use increases the risk of dry mouth, constipation, urinary retention, blurred vision, tachycardia, confusion, and delirium. Older patients are especially vulnerable to cognitive effects and heat intolerance.
How serious is the interaction between Tolterodine 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: Avoid the combination in older or cognitively impaired patients where possible. If it is used, monitor for confusion, urinary retention, and constipation and use the lowest effective doses.
What other medicines interact with Tolterodine?
MediHelp also lists interactions of Tolterodine with, for example, Clarithromycin, Clozapine, Cobicistat. The full list is on the Tolterodine page.
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