Drug interactions
Hydrochlorothiazide-losartan + Phenobarbital
Severity: Moderate
Hydrochlorothiazide-losartan and Phenobarbital: 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
Phenobarbital induces CYP enzymes including CYP2C9 and CYP3A4, which may lower losartan and active metabolite levels and weaken blood pressure control. Phenobarbital may also add to orthostatic hypotension with diuretics.
What this interaction means in plain words
Hydrochlorothiazide-losartan and Phenobarbital 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.
Why it happens
Induction of CYP2C9 and CYP3A4 increases losartan clearance.
What to do
Monitor blood pressure after phenobarbital is started or stopped and titrate losartan accordingly.
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
Frequently asked questions
Can I take Hydrochlorothiazide-losartan with Phenobarbital?
MediHelp rates the interaction as moderate. Hydrochlorothiazide-losartan and Phenobarbital 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. Phenobarbital induces CYP enzymes including CYP2C9 and CYP3A4, which may lower losartan and active metabolite levels and weaken blood pressure control. Phenobarbital may also add to orthostatic hypotension with diuretics.
How serious is the interaction between Hydrochlorothiazide-losartan and Phenobarbital?
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 after phenobarbital is started or stopped and titrate losartan accordingly.
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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