Drug interactions
Bosentan + Fosphenytoin
Severity: Moderate
Bosentan and Fosphenytoin: 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
Phenytoin, the active form of fosphenytoin, is cleared by CYP2C9 and CYP2C19, and bosentan may increase its clearance. Phenytoin also induces CYP3A4 and CYP2C9 and may reduce bosentan exposure. Both drugs may lose efficacy, and phenytoin has a narrow therapeutic range.
What this interaction means in plain words
Bosentan and Fosphenytoin 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.
Bosentan belongs to Miscellaneous; Fosphenytoin belongs to Central Nervous System.
Why it happens
Bosentan induces CYP2C9 and CYP3A4, and phenytoin reciprocally induces bosentan metabolism.
What to do
Monitor phenytoin levels and seizure control, and watch for reduced bosentan response in pulmonary arterial hypertension.
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 Bosentan
- Bosentan + Cyclosporin Contraindicated
- Bosentan + Glibenclamide Contraindicated
- Bosentan + Glyburide-metformin Contraindicated
- Bosentan + Lonafarnib Contraindicated
- Bosentan + Sparsentan Contraindicated
- Artemether / lumefantrine + Bosentan Major
Other interactions of Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Bosentan with Fosphenytoin?
MediHelp rates the interaction as moderate. Bosentan and Fosphenytoin 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. Phenytoin, the active form of fosphenytoin, is cleared by CYP2C9 and CYP2C19, and bosentan may increase its clearance. Phenytoin also induces CYP3A4 and CYP2C9 and may reduce bosentan exposure. Both drugs may lose efficacy, and phenytoin has a narrow therapeutic range.
How serious is the interaction between Bosentan and Fosphenytoin?
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 phenytoin levels and seizure control, and watch for reduced bosentan response in pulmonary arterial hypertension.
What other medicines interact with Bosentan?
MediHelp also lists interactions of Bosentan with, for example, Cyclosporin, Glibenclamide, Glyburide-metformin. The full list is on the Bosentan page.
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