Drug interactions
Telmisartan + Trimethoprim
Severity: Major
Telmisartan 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, impairing potassium excretion, and telmisartan lowers aldosterone effect. Combined use can produce significant hyperkalemia, especially in older patients or those with renal impairment.
What this interaction means in plain words
Telmisartan 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.
Telmisartan belongs to Cardiovascular; Trimethoprim belongs to Anti Bacterial.
Why it happens
Trimethoprim has a potassium-sparing, amiloride-like action that adds to the reduced potassium excretion from angiotensin receptor blockade.
What to do
Check serum potassium and creatinine within several days of starting trimethoprim, and choose another antibiotic where possible. Avoid in patients with renal impairment or existing hyperkalemia.
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 Telmisartan
- Aliskiren + Telmisartan Contraindicated
- Sparsentan + Telmisartan Contraindicated
- Amifostine + Telmisartan Major
- Amiloride + Telmisartan Major
- Amlodipine-benazepril + Telmisartan Major
- Amlodipine-hydrochlorothiazide-valsartan + Telmisartan Major
Other interactions of Trimethoprim
Frequently asked questions
Can I take Telmisartan with Trimethoprim?
MediHelp rates the interaction as major. Telmisartan 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, impairing potassium excretion, and telmisartan lowers aldosterone effect. Combined use can produce significant hyperkalemia, especially in older patients or those with renal impairment.
How serious is the interaction between Telmisartan 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 choose another antibiotic where possible. Avoid in patients with renal impairment or existing hyperkalemia.
What other medicines interact with Telmisartan?
MediHelp also lists interactions of Telmisartan with, for example, Aliskiren, Sparsentan, Amifostine. The full list is on the Telmisartan page.
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