Drug interactions
Hydrochlorothiazide-irbesartan + Trimethoprim
Severity: Major
Hydrochlorothiazide-irbesartan and Trimethoprim: 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
Trimethoprim blocks epithelial sodium channels in the distal nephron, reducing potassium excretion, and irbesartan lowers aldosterone-mediated potassium excretion. Together they can cause clinically significant hyperkalemia, especially in older patients, those with renal impairment or diabetes, or on high trimethoprim doses. The thiazide component lowers potassium and may partly offset this, but it does not reliably prevent hyperkalemia.
What this interaction means in plain words
Hydrochlorothiazide-irbesartan and Trimethoprim 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.
Hydrochlorothiazide-irbesartan belongs to Cardiovascular; Trimethoprim belongs to Anti Bacterial.
Why it happens
Additive potassium retention through ENaC blockade by trimethoprim and angiotensin receptor blockade by irbesartan.
What to do
Check serum potassium and creatinine within several days of starting trimethoprim and periodically afterward, particularly in renal impairment. Consider an alternative antibiotic in high-risk patients.
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 Hydrochlorothiazide-irbesartan
- Aliskiren + Hydrochlorothiazide-irbesartan Contraindicated
- Dofetilide + Hydrochlorothiazide-irbesartan Contraindicated
- Hydrochlorothiazide-irbesartan + Sparsentan Contraindicated
- Aldesleukin + Hydrochlorothiazide-irbesartan Major
- Amifostine + Hydrochlorothiazide-irbesartan Major
- Amiloride + Hydrochlorothiazide-irbesartan Major
Other interactions of Trimethoprim
Frequently asked questions
Can I take Hydrochlorothiazide-irbesartan with Trimethoprim?
MediHelp rates the interaction as major. Hydrochlorothiazide-irbesartan and Trimethoprim 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. Trimethoprim blocks epithelial sodium channels in the distal nephron, reducing potassium excretion, and irbesartan lowers aldosterone-mediated potassium excretion. Together they can cause clinically significant hyperkalemia, especially in older patients, those with renal impairment or diabetes, or on high trimethoprim doses. The thiazide component lowers potassium and may partly offset this, but it does not reliably prevent hyperkalemia.
How serious is the interaction between Hydrochlorothiazide-irbesartan and Trimethoprim?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Check serum potassium and creatinine within several days of starting trimethoprim and periodically afterward, particularly in renal impairment. Consider an alternative antibiotic in high-risk patients.
What other medicines interact with Hydrochlorothiazide-irbesartan?
MediHelp also lists interactions of Hydrochlorothiazide-irbesartan with, for example, Aliskiren, Dofetilide, Sparsentan. The full list is on the Hydrochlorothiazide-irbesartan page.
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