Drug interactions
Doxepin + Trihexyphenidyl
Severity: Moderate
Doxepin 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
Doxepin, a tricyclic antidepressant, has substantial antimuscarinic activity, and combined with trihexyphenidyl the anticholinergic burden can become excessive. This may cause constipation, urinary retention, confusion, delirium, blurred vision and tachycardia.
What this interaction means in plain words
Doxepin 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.
Doxepin belongs to Dermatology; Trihexyphenidyl belongs to Central Nervous System.
Why it happens
Additive muscarinic receptor blockade.
What to do
Monitor for anticholinergic toxicity, particularly cognition and bowel and bladder function in older adults; consider reducing doses or using a less anticholinergic antidepressant.
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 Trihexyphenidyl
Other interactions of Doxepin
- Doxepin + Isocarboxazid Contraindicated
- Doxepin + Phenelzine Contraindicated
- Doxepin + Procarbazine Contraindicated
- Doxepin + Safinamide Contraindicated
- Doxepin + Selegiline Contraindicated
- Doxepin + Tranylcypromine Contraindicated
Frequently asked questions
Can I take Doxepin with Trihexyphenidyl?
MediHelp rates the interaction as moderate. Doxepin 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. Doxepin, a tricyclic antidepressant, has substantial antimuscarinic activity, and combined with trihexyphenidyl the anticholinergic burden can become excessive. This may cause constipation, urinary retention, confusion, delirium, blurred vision and tachycardia.
How serious is the interaction between Doxepin 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, particularly cognition and bowel and bladder function in older adults; consider reducing doses or using a less anticholinergic antidepressant.
What other medicines interact with Trihexyphenidyl?
MediHelp also lists interactions of Trihexyphenidyl with, for example, Orphenadrin, Oxybutynin, Scopolamine. The full list is on the Trihexyphenidyl page.
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