Drug interactions
Isoniazid + Tolvaptan
Severity: Moderate
Isoniazid 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
Tolvaptan is a CYP3A4 substrate, and potent inhibitors markedly increase its exposure, risking too rapid a rise in serum sodium. Isoniazid is a weak to moderate inhibitor, so the effect is expected to be smaller but is not well quantified.
What this interaction means in plain words
Isoniazid 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.
Isoniazid belongs to Anti Bacterial; Tolvaptan belongs to Endocrine.
Why it happens
Isoniazid may inhibit CYP3A4-mediated metabolism of tolvaptan, increasing its exposure.
What to do
Monitor serum sodium frequently, especially in the first days of combined therapy, to avoid overly rapid correction. Reduce the tolvaptan dose or interrupt it if the sodium rise is too fast.
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 Isoniazid
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 Isoniazid with Tolvaptan?
MediHelp rates the interaction as moderate. Isoniazid 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. Tolvaptan is a CYP3A4 substrate, and potent inhibitors markedly increase its exposure, risking too rapid a rise in serum sodium. Isoniazid is a weak to moderate inhibitor, so the effect is expected to be smaller but is not well quantified.
How serious is the interaction between Isoniazid 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 frequently, especially in the first days of combined therapy, to avoid overly rapid correction. Reduce the tolvaptan dose or interrupt it if the sodium rise is too fast.
What other medicines interact with Isoniazid?
MediHelp also lists interactions of Isoniazid with, for example, Bacillus calmette-guerin substrain tice, Benzhydrocodone / acetaminophen, Carbamazepine. The full list is on the Isoniazid page.
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