Drug interactions
Diphenoxylate-atropine + Promethazine
Severity: Moderate
Diphenoxylate-atropine and Promethazine: 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
Promethazine is strongly sedating and anticholinergic, which adds to the opioid and atropine effects of diphenoxylate-atropine. Marked drowsiness, respiratory depression in vulnerable patients, constipation, urinary retention and confusion can occur.
What this interaction means in plain words
Diphenoxylate-atropine and Promethazine 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-atropine belongs to Gastrointestinal Tract; Promethazine belongs to Respiratory.
Why it happens
Additive CNS depression and antimuscarinic effects.
What to do
Monitor for sedation, respiratory depression and anticholinergic effects, and use reduced doses in older or frail patients. Avoid in young children because of respiratory depression risk.
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 Diphenoxylate-atropine
- Diphenoxylate-atropine + Isocarboxazid Contraindicated
- Diphenoxylate-atropine + Phenelzine Contraindicated
- Diphenoxylate-atropine + Tranylcypromine Contraindicated
- Alfentanil + Diphenoxylate-atropine Major
- Alvimopan + Diphenoxylate-atropine Major
- Amitriptyline + Diphenoxylate-atropine Major
Other interactions of Promethazine
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
Frequently asked questions
Can I take Diphenoxylate-atropine with Promethazine?
MediHelp rates the interaction as moderate. Diphenoxylate-atropine and Promethazine 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. Promethazine is strongly sedating and anticholinergic, which adds to the opioid and atropine effects of diphenoxylate-atropine. Marked drowsiness, respiratory depression in vulnerable patients, constipation, urinary retention and confusion can occur.
How serious is the interaction between Diphenoxylate-atropine and Promethazine?
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 sedation, respiratory depression and anticholinergic effects, and use reduced doses in older or frail patients. Avoid in young children because of respiratory depression risk.
What other medicines interact with Diphenoxylate-atropine?
MediHelp also lists interactions of Diphenoxylate-atropine with, for example, Isocarboxazid, Phenelzine, Tranylcypromine. The full list is on the Diphenoxylate-atropine page.
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