Drug interactions
Scopolamine + Trihexyphenidyl
Severity: Major
Scopolamine and Trihexyphenidyl: major 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 are potent antimuscarinics, so combining them can produce marked anticholinergic toxicity with dry mouth, constipation, urinary retention, blurred vision, tachycardia, confusion and hallucinations. Older adults are especially susceptible, and hyperthermia can occur.
What this interaction means in plain words
Scopolamine and Trihexyphenidyl can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Scopolamine belongs to Respiratory; Trihexyphenidyl belongs to Central Nervous System.
Why it happens
Additive muscarinic receptor blockade in the central and peripheral nervous systems.
What to do
Avoid the combination where possible, particularly in older adults. If it is necessary, use the lowest doses and monitor for delirium, retention and tachycardia.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Scopolamine
Other interactions of Trihexyphenidyl
Frequently asked questions
Can I take Scopolamine with Trihexyphenidyl?
MediHelp rates the interaction as major. Scopolamine and Trihexyphenidyl can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Both are potent antimuscarinics, so combining them can produce marked anticholinergic toxicity with dry mouth, constipation, urinary retention, blurred vision, tachycardia, confusion and hallucinations. Older adults are especially susceptible, and hyperthermia can occur.
How serious is the interaction between Scopolamine and Trihexyphenidyl?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination where possible, particularly in older adults. If it is necessary, use the lowest doses and monitor for delirium, retention and tachycardia.
What other medicines interact with Scopolamine?
MediHelp also lists interactions of Scopolamine with, for example, Benzhydrocodone / acetaminophen, Buprenorphine long-acting, Buprenorphine subdermal implant. The full list is on the Scopolamine page.
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