Drug interactions
Quetiapine + Trihexyphenidyl
Severity: Moderate
Quetiapine 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
Quetiapine has some anticholinergic activity through its metabolite norquetiapine, which can add to the effects of trihexyphenidyl. This may cause dry mouth, constipation, urinary retention, blurred vision, confusion and tachycardia, especially in older patients.
What this interaction means in plain words
Quetiapine 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.
Quetiapine belongs to Central Nervous System; Trihexyphenidyl belongs to Central Nervous System.
Why it happens
Additive anticholinergic (muscarinic antagonist) pharmacodynamic effects.
What to do
Monitor for anticholinergic toxicity such as confusion, urinary retention and constipation. Use the lowest effective trihexyphenidyl dose and reassess the need for it regularly.
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 Quetiapine
- Adagrasib + Quetiapine Major
- Amiodarone + Quetiapine Major
- Amisulpride + Quetiapine Major
- Amoxapine + Quetiapine Major
- Anagrelide + Quetiapine Major
- Apalutamide + Quetiapine Major
Other interactions of Trihexyphenidyl
Frequently asked questions
Can I take Quetiapine with Trihexyphenidyl?
MediHelp rates the interaction as moderate. Quetiapine 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. Quetiapine has some anticholinergic activity through its metabolite norquetiapine, which can add to the effects of trihexyphenidyl. This may cause dry mouth, constipation, urinary retention, blurred vision, confusion and tachycardia, especially in older patients.
How serious is the interaction between Quetiapine 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 such as confusion, urinary retention and constipation. Use the lowest effective trihexyphenidyl dose and reassess the need for it regularly.
What other medicines interact with Quetiapine?
MediHelp also lists interactions of Quetiapine with, for example, Adagrasib, Amiodarone, Amisulpride. The full list is on the Quetiapine page.
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