Drug interactions
Ritonavir + Tolterodine
Severity: Moderate
Ritonavir 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
Ritonavir is a strong CYP3A4 inhibitor and raises tolterodine exposure, particularly in CYP2D6 poor metabolizers. This increases anticholinergic adverse effects and may increase QT prolongation risk.
What this interaction means in plain words
Ritonavir 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.
Ritonavir belongs to Anti Virals; Tolterodine belongs to Genitourinary.
Why it happens
Inhibition of CYP3A4 by ritonavir reduces tolterodine clearance.
What to do
Cap tolterodine at 1 mg twice daily during potent CYP3A4 inhibitor therapy, as per labeling. Monitor for anticholinergic effects and QT risk factors.
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 Tolterodine
Other interactions of Ritonavir
- Alfuzosin + Ritonavir Contraindicated
- Amiodarone + Ritonavir Contraindicated
- Avanafil + Ritonavir Contraindicated
- Colchicine + Ritonavir Contraindicated
- Dronedarone + Ritonavir Contraindicated
- Eletriptan + Ritonavir Contraindicated
Frequently asked questions
Can I take Ritonavir with Tolterodine?
MediHelp rates the interaction as moderate. Ritonavir 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. Ritonavir is a strong CYP3A4 inhibitor and raises tolterodine exposure, particularly in CYP2D6 poor metabolizers. This increases anticholinergic adverse effects and may increase QT prolongation risk.
How serious is the interaction between Ritonavir 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: Cap tolterodine at 1 mg twice daily during potent CYP3A4 inhibitor therapy, as per labeling. Monitor for anticholinergic effects and QT risk factors.
What other medicines interact with Tolterodine?
MediHelp also lists interactions of Tolterodine with, for example, Clarithromycin, Clozapine, Cobicistat. The full list is on the Tolterodine page.
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