Drug interactions
Difenoxin + Promethazine
Severity: Moderate
Difenoxin 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
Difenoxin is an opioid antidiarrheal metabolite related to diphenoxylate, and promethazine can add to its CNS depressant effects. This may cause excessive drowsiness and, at higher doses, respiratory depression, with added anticholinergic effects on the gut.
What this interaction means in plain words
Difenoxin 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.
Difenoxin belongs to Gastrointestinal Tract; Promethazine belongs to Respiratory.
Why it happens
Additive CNS depression from opioid agonism and H1 antagonism, with additive antimuscarinic effects.
What to do
Monitor for sedation and reduced bowel motility, and avoid exceeding recommended doses; counsel against driving.
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 Promethazine
- Cabergoline + Promethazine Contraindicated
- Dopamine + Promethazine Contraindicated
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
Other interactions of Difenoxin
Frequently asked questions
Can I take Difenoxin with Promethazine?
MediHelp rates the interaction as moderate. Difenoxin 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. Difenoxin is an opioid antidiarrheal metabolite related to diphenoxylate, and promethazine can add to its CNS depressant effects. This may cause excessive drowsiness and, at higher doses, respiratory depression, with added anticholinergic effects on the gut.
How serious is the interaction between Difenoxin 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 and reduced bowel motility, and avoid exceeding recommended doses; counsel against driving.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Cabergoline, Dopamine, Ibutilide. The full list is on the Promethazine page.
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