Drug interactions
Phenobarbital + Tolvaptan
Severity: Moderate
Phenobarbital and Tolvaptan: 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
Phenobarbital is a CYP3A4 inducer and can substantially reduce tolvaptan exposure. The result may be inadequate correction of hyponatremia or reduced efficacy in ADPKD.
What this interaction means in plain words
Phenobarbital and Tolvaptan 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
Induction of CYP3A4 increases tolvaptan metabolism.
What to do
Monitor serum sodium and therapeutic response, and adjust the tolvaptan dose upward if needed. Prefer a non-inducing anticonvulsant where feasible.
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 Tolvaptan
- Atazanavir + Tolvaptan Contraindicated
- Ceritinib + Tolvaptan Contraindicated
- Cobicistat + Tolvaptan Contraindicated
- Conivaptan + Tolvaptan Contraindicated
- Darunavir + Tolvaptan Contraindicated
- Idelalisib + Tolvaptan Contraindicated
Frequently asked questions
Can I take Phenobarbital with Tolvaptan?
MediHelp rates the interaction as moderate. Phenobarbital and Tolvaptan 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. Phenobarbital is a CYP3A4 inducer and can substantially reduce tolvaptan exposure. The result may be inadequate correction of hyponatremia or reduced efficacy in ADPKD.
How serious is the interaction between Phenobarbital and Tolvaptan?
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 serum sodium and therapeutic response, and adjust the tolvaptan dose upward if needed. Prefer a non-inducing anticonvulsant where feasible.
What other medicines interact with Tolvaptan?
MediHelp also lists interactions of Tolvaptan with, for example, Atazanavir, Ceritinib, Cobicistat. The full list is on the Tolvaptan page.
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