Drug interactions
Isosorbide mononitrate + Phenytoin
Severity: Minor
Isosorbide mononitrate and Phenytoin: minor 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 is an enzyme inducer and could lower nitrate exposure, but isosorbide mononitrate is not mainly cleared by CYP3A4. A meaningful loss of antianginal efficacy is possible but poorly documented.
What this interaction means in plain words
Isosorbide mononitrate and Phenytoin have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Isosorbide mononitrate belongs to Cardiovascular; Phenytoin belongs to Central Nervous System.
Why it happens
Hepatic enzyme induction by phenytoin may modestly increase nitrate clearance.
What to do
Monitor angina control and adjust the nitrate dose if symptoms worsen.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Isosorbide mononitrate and Phenytoin, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Isosorbide mononitrate
- Avanafil + Isosorbide mononitrate Contraindicated
- Isosorbide mononitrate + Riociguat Contraindicated
- Isosorbide mononitrate + Sildenafil Contraindicated
- Isosorbide mononitrate + Tadalafil Contraindicated
- Isosorbide mononitrate + Vardenafil Contraindicated
- Ergotamine + Isosorbide mononitrate Major
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
Frequently asked questions
Can I take Isosorbide mononitrate with Phenytoin?
MediHelp rates the interaction as minor. Isosorbide mononitrate and Phenytoin have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Phenytoin is an enzyme inducer and could lower nitrate exposure, but isosorbide mononitrate is not mainly cleared by CYP3A4. A meaningful loss of antianginal efficacy is possible but poorly documented.
How serious is the interaction between Isosorbide mononitrate and Phenytoin?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor angina control and adjust the nitrate dose if symptoms worsen.
What other medicines interact with Isosorbide mononitrate?
MediHelp also lists interactions of Isosorbide mononitrate with, for example, Avanafil, Riociguat, Sildenafil. The full list is on the Isosorbide mononitrate page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
