Drug interactions
Promethazine + Tolterodine
Severity: Moderate
Promethazine and Tolterodine: 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 block muscarinic receptors, so combining them increases dry mouth, constipation, urinary retention, blurred vision and confusion, especially in older patients.
What this interaction means in plain words
Promethazine and Tolterodine 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 belongs to Respiratory; Tolterodine belongs to Genitourinary.
Why it happens
Additive muscarinic receptor antagonism.
What to do
Monitor for anticholinergic burden and cognitive effects, and avoid the combination in frail elderly patients where possible.
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 Tolterodine
Frequently asked questions
Can I take Promethazine with Tolterodine?
MediHelp rates the interaction as moderate. Promethazine and Tolterodine 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 block muscarinic receptors, so combining them increases dry mouth, constipation, urinary retention, blurred vision and confusion, especially in older patients.
How serious is the interaction between Promethazine and Tolterodine?
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 burden and cognitive effects, and avoid the combination in frail elderly patients where possible.
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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