Drug interactions
Hydrochlorothiazide-valsartan + Trimethoprim
Severity: Major
Hydrochlorothiazide-valsartan 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 reduces renal potassium excretion in a way similar to amiloride, and valsartan also raises potassium. Together they can cause clinically significant hyperkalemia, especially in elderly patients, those with renal impairment, or with high-dose trimethoprim. The thiazide partly offsets this but does not remove the risk.
What this interaction means in plain words
Hydrochlorothiazide-valsartan 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-valsartan belongs to Cardiovascular; Trimethoprim belongs to Anti Bacterial.
Why it happens
Trimethoprim blocks epithelial sodium channels in the distal nephron while valsartan reduces aldosterone effect, together impairing potassium excretion.
What to do
Check serum potassium and creatinine within the first week of co-therapy and periodically thereafter. Consider an alternative antibiotic in patients with renal impairment or other hyperkalemia risk factors.
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-valsartan
- Aliskiren + Hydrochlorothiazide-valsartan Contraindicated
- Dofetilide + Hydrochlorothiazide-valsartan Contraindicated
- Hydrochlorothiazide-valsartan + Sparsentan Contraindicated
- Aldesleukin + Hydrochlorothiazide-valsartan Major
- Amifostine + Hydrochlorothiazide-valsartan Major
- Amiloride + Hydrochlorothiazide-valsartan Major
Other interactions of Trimethoprim
Frequently asked questions
Can I take Hydrochlorothiazide-valsartan with Trimethoprim?
MediHelp rates the interaction as major. Hydrochlorothiazide-valsartan 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 reduces renal potassium excretion in a way similar to amiloride, and valsartan also raises potassium. Together they can cause clinically significant hyperkalemia, especially in elderly patients, those with renal impairment, or with high-dose trimethoprim. The thiazide partly offsets this but does not remove the risk.
How serious is the interaction between Hydrochlorothiazide-valsartan 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 the first week of co-therapy and periodically thereafter. Consider an alternative antibiotic in patients with renal impairment or other hyperkalemia risk factors.
What other medicines interact with Hydrochlorothiazide-valsartan?
MediHelp also lists interactions of Hydrochlorothiazide-valsartan with, for example, Aliskiren, Dofetilide, Sparsentan. The full list is on the Hydrochlorothiazide-valsartan page.
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