Drug interactions
Oxybutynin + Promethazine
Severity: Moderate
Oxybutynin 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
Both drugs have strong anticholinergic activity, so combining them increases dry mouth, constipation, urinary retention, blurred vision, confusion and heat intolerance. Older patients are especially vulnerable to cognitive effects.
What this interaction means in plain words
Oxybutynin 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.
Oxybutynin belongs to Genitourinary; Promethazine belongs to Respiratory.
Why it happens
Additive muscarinic receptor antagonism.
What to do
Avoid the combination in older or cognitively impaired patients where possible. Monitor for anticholinergic toxicity and consider alternatives.
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
- Ibutilide + Promethazine Contraindicated
- Pimozide + Promethazine Contraindicated
- Promethazine + Thioridazine Contraindicated
- Alfentanil + Promethazine Major
- Amiodarone + Promethazine Major
- Amisulpride + Promethazine Major
Other interactions of Oxybutynin
Frequently asked questions
Can I take Oxybutynin with Promethazine?
MediHelp rates the interaction as moderate. Oxybutynin 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. Both drugs have strong anticholinergic activity, so combining them increases dry mouth, constipation, urinary retention, blurred vision, confusion and heat intolerance. Older patients are especially vulnerable to cognitive effects.
How serious is the interaction between Oxybutynin 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: Avoid the combination in older or cognitively impaired patients where possible. Monitor for anticholinergic toxicity and consider alternatives.
What other medicines interact with Promethazine?
MediHelp also lists interactions of Promethazine with, for example, Ibutilide, Pimozide, Thioridazine. The full list is on the Promethazine page.
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