Drug interactions
Macitentan + Phenytoin
Severity: Major
Macitentan and Phenytoin: major 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
Strong CYP3A4 inducers substantially reduce macitentan exposure, which may reduce effectiveness in pulmonary arterial hypertension.
What this interaction means in plain words
Macitentan and Phenytoin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Macitentan belongs to Cardiovascular; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4, increasing macitentan and active metabolite clearance.
What to do
Avoid the combination and use a non-inducing antiseizure drug. If unavoidable, monitor symptoms, functional class and hemodynamic status.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Phenytoin
- Artemether / lumefantrine + Phenytoin Contraindicated
- Bictegravir + Phenytoin Contraindicated
- Cabotegravir + Phenytoin Contraindicated
- Doravirine + Phenytoin Contraindicated
- Elbasvir / grazoprevir + Phenytoin Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Phenytoin Contraindicated
Other interactions of Macitentan
- Amiodarone + Macitentan Major
- Apalutamide + Macitentan Major
- Bosentan + Macitentan Major
- Carbamazepine + Macitentan Major
- Clarithromycin + Macitentan Major
- Efavirenz + Macitentan Major
Frequently asked questions
Can I take Macitentan with Phenytoin?
MediHelp rates the interaction as major. Macitentan and Phenytoin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Strong CYP3A4 inducers substantially reduce macitentan exposure, which may reduce effectiveness in pulmonary arterial hypertension.
How serious is the interaction between Macitentan and Phenytoin?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination and use a non-inducing antiseizure drug. If unavoidable, monitor symptoms, functional class and hemodynamic status.
What other medicines interact with Phenytoin?
MediHelp also lists interactions of Phenytoin with, for example, Artemether / lumefantrine, Bictegravir, Cabotegravir. The full list is on the Phenytoin page.
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