Drug interactions
Darifenacin + Tucatinib
Severity: Moderate
Darifenacin and Tucatinib: 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
Tucatinib inhibits CYP3A4 and may raise darifenacin concentrations, increasing anticholinergic adverse effects such as dry mouth, constipation, and urinary retention. Darifenacin is a sensitive CYP3A4 substrate, so the effect may be clinically relevant.
What this interaction means in plain words
Darifenacin and Tucatinib 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.
Darifenacin belongs to Genitourinary; Tucatinib belongs to Oncology.
Why it happens
Inhibition of CYP3A4-mediated metabolism of darifenacin by tucatinib.
What to do
Monitor for anticholinergic toxicity and limit darifenacin to the lowest effective dose, not exceeding the labeled maximum for use with moderate CYP3A4 inhibitors. Consider an alternative bladder agent if effects are problematic.
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 Darifenacin
Other interactions of Tucatinib
- Cisapride + Tucatinib Contraindicated
- Eletriptan + Tucatinib Contraindicated
- Ergotamine + Tucatinib Contraindicated
- Flibanserin + Tucatinib Contraindicated
- Ranolazine + Tucatinib Contraindicated
- Amobarbital + Tucatinib Major
Frequently asked questions
Can I take Darifenacin with Tucatinib?
MediHelp rates the interaction as moderate. Darifenacin and Tucatinib 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. Tucatinib inhibits CYP3A4 and may raise darifenacin concentrations, increasing anticholinergic adverse effects such as dry mouth, constipation, and urinary retention. Darifenacin is a sensitive CYP3A4 substrate, so the effect may be clinically relevant.
How serious is the interaction between Darifenacin and Tucatinib?
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 toxicity and limit darifenacin to the lowest effective dose, not exceeding the labeled maximum for use with moderate CYP3A4 inhibitors. Consider an alternative bladder agent if effects are problematic.
What other medicines interact with Darifenacin?
MediHelp also lists interactions of Darifenacin with, for example, Atazanavir, Bethanechol, Clarithromycin. The full list is on the Darifenacin page.
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