Drug interactions
Diphenoxylate + Doxylamine
Severity: Moderate
Diphenoxylate and Doxylamine: 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
Doxylamine is a sedating antihistamine and diphenoxylate is an opioid antidiarrheal that can cause CNS depression at higher doses. Taken together they may produce additive drowsiness and impaired psychomotor performance. Anticholinergic effects on the gut may also add up.
What this interaction means in plain words
Diphenoxylate and Doxylamine 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.
Diphenoxylate belongs to Gastrointestinal Tract; Doxylamine belongs to Respiratory.
Why it happens
Additive CNS depressant effects, with additive anticholinergic activity.
What to do
Counsel the patient to avoid driving or hazardous tasks until the response is known, and keep diphenoxylate at the labeled dose. Watch for excessive sedation, urinary retention and constipation or ileus.
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 Doxylamine
Other interactions of Diphenoxylate
Frequently asked questions
Can I take Diphenoxylate with Doxylamine?
MediHelp rates the interaction as moderate. Diphenoxylate and Doxylamine 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. Doxylamine is a sedating antihistamine and diphenoxylate is an opioid antidiarrheal that can cause CNS depression at higher doses. Taken together they may produce additive drowsiness and impaired psychomotor performance. Anticholinergic effects on the gut may also add up.
How serious is the interaction between Diphenoxylate and Doxylamine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Counsel the patient to avoid driving or hazardous tasks until the response is known, and keep diphenoxylate at the labeled dose. Watch for excessive sedation, urinary retention and constipation or ileus.
What other medicines interact with Doxylamine?
MediHelp also lists interactions of Doxylamine with, for example, Belladonna and opium, Benzhydrocodone / acetaminophen, Brexanolone. The full list is on the Doxylamine page.
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