Drug interactions
Hydrochlorothiazide-olmesartan + Trimethoprim
Severity: Major
Hydrochlorothiazide-olmesartan 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 and reduces potassium excretion, and olmesartan reduces aldosterone-mediated potassium excretion. Hyperkalemia can result, especially with high trimethoprim doses, renal impairment or older age. Hydrochlorothiazide partly offsets this effect but does not remove the risk.
What this interaction means in plain words
Hydrochlorothiazide-olmesartan 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-olmesartan belongs to Cardiovascular; Trimethoprim belongs to Anti Bacterial.
Why it happens
Additive reduction of renal potassium excretion through ENaC blockade by trimethoprim and RAAS inhibition by olmesartan.
What to do
Check serum potassium and creatinine within several days of starting trimethoprim, and 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-olmesartan
- Aliskiren + Hydrochlorothiazide-olmesartan Contraindicated
- Dofetilide + Hydrochlorothiazide-olmesartan Contraindicated
- Hydrochlorothiazide-olmesartan + Sparsentan Contraindicated
- Acemetacin + Hydrochlorothiazide-olmesartan Major
- Amifostine + Hydrochlorothiazide-olmesartan Major
- Amiloride + Hydrochlorothiazide-olmesartan Major
Other interactions of Trimethoprim
Frequently asked questions
Can I take Hydrochlorothiazide-olmesartan with Trimethoprim?
MediHelp rates the interaction as major. Hydrochlorothiazide-olmesartan 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 and reduces potassium excretion, and olmesartan reduces aldosterone-mediated potassium excretion. Hyperkalemia can result, especially with high trimethoprim doses, renal impairment or older age. Hydrochlorothiazide partly offsets this effect but does not remove the risk.
How serious is the interaction between Hydrochlorothiazide-olmesartan 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 consider an alternative antibiotic in high-risk patients.
What other medicines interact with Hydrochlorothiazide-olmesartan?
MediHelp also lists interactions of Hydrochlorothiazide-olmesartan with, for example, Aliskiren, Dofetilide, Sparsentan. The full list is on the Hydrochlorothiazide-olmesartan page.
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