Drug interactions
Phenytoin + Riociguat
Severity: Moderate
Phenytoin and Riociguat: 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 may lower riociguat concentrations, potentially reducing its benefit in pulmonary hypertension.
What this interaction means in plain words
Phenytoin and Riociguat 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 belongs to Central Nervous System; Riociguat belongs to Cardiovascular.
Why it happens
Induction of CYP3A4 and other enzymes by phenytoin increases riociguat clearance.
What to do
Monitor clinical response and consider titrating riociguat upward. Reassess dosing if phenytoin is stopped.
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 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 Riociguat
- Avanafil + Riociguat Contraindicated
- Dipyridamole + Riociguat Contraindicated
- Isosorbide dinitrate + Riociguat Contraindicated
- Isosorbide mononitrate + Riociguat Contraindicated
- Nitroglycerin + Riociguat Contraindicated
- Riociguat + Sildenafil Contraindicated
Frequently asked questions
Can I take Phenytoin with Riociguat?
MediHelp rates the interaction as moderate. Phenytoin and Riociguat 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 may lower riociguat concentrations, potentially reducing its benefit in pulmonary hypertension.
How serious is the interaction between Phenytoin and Riociguat?
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 clinical response and consider titrating riociguat upward. Reassess dosing if phenytoin is stopped.
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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