Drug interactions
Oxybutynin transdermal + Promethazine
Severity: Moderate
Oxybutynin transdermal 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
Oxybutynin is an antimuscarinic and promethazine has substantial anticholinergic activity. Combined use can increase dry mouth, constipation, urinary retention, blurred vision, drowsiness and confusion, even though the patch avoids first-pass metabolism.
What this interaction means in plain words
Oxybutynin transdermal 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.
Why it happens
Additive antimuscarinic effects.
What to do
Monitor for anticholinergic adverse effects, especially in older adults and those with cognitive impairment. Reduce the dose or choose a less anticholinergic alternative if symptoms develop.
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
Frequently asked questions
Can I take Oxybutynin transdermal with Promethazine?
MediHelp rates the interaction as moderate. Oxybutynin transdermal 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 is an antimuscarinic and promethazine has substantial anticholinergic activity. Combined use can increase dry mouth, constipation, urinary retention, blurred vision, drowsiness and confusion, even though the patch avoids first-pass metabolism.
How serious is the interaction between Oxybutynin transdermal 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 anticholinergic adverse effects, especially in older adults and those with cognitive impairment. Reduce the dose or choose a less anticholinergic alternative if symptoms develop.
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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