Drug interactions
Hydrochlorothiazide-losartan + Phenytoin
Severity: Moderate
Hydrochlorothiazide-losartan and Phenytoin: 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 induces hepatic enzymes and may lower plasma levels of losartan and its active metabolite, potentially weakening blood pressure control. Evidence is limited and the effect is generally modest.
What this interaction means in plain words
Hydrochlorothiazide-losartan and Phenytoin 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.
Hydrochlorothiazide-losartan belongs to Cardiovascular; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induction of CYP2C9 and CYP3A4 may increase losartan metabolism.
What to do
Monitor blood pressure when phenytoin is started, stopped or changed in dose, and adjust the losartan dose if control is lost.
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 Hydrochlorothiazide-losartan
- Aliskiren + Hydrochlorothiazide-losartan Contraindicated
- Dofetilide + Hydrochlorothiazide-losartan Contraindicated
- Hydrochlorothiazide-losartan + Sparsentan Contraindicated
- Aceclofenac + Hydrochlorothiazide-losartan Major
- Aldesleukin + Hydrochlorothiazide-losartan Major
- Amifostine + Hydrochlorothiazide-losartan 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 Hydrochlorothiazide-losartan with Phenytoin?
MediHelp rates the interaction as moderate. Hydrochlorothiazide-losartan and Phenytoin 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 induces hepatic enzymes and may lower plasma levels of losartan and its active metabolite, potentially weakening blood pressure control. Evidence is limited and the effect is generally modest.
How serious is the interaction between Hydrochlorothiazide-losartan and Phenytoin?
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 blood pressure when phenytoin is started, stopped or changed in dose, and adjust the losartan dose if control is lost.
What other medicines interact with Hydrochlorothiazide-losartan?
MediHelp also lists interactions of Hydrochlorothiazide-losartan with, for example, Aliskiren, Dofetilide, Sparsentan. The full list is on the Hydrochlorothiazide-losartan page.
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