Drug interactions
Olmesartan + Trimethoprim
Severity: Major
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 lowers aldosterone effect. Together they can cause marked hyperkalemia, especially in older patients or those with renal impairment.
What this interaction means in plain words
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.
Olmesartan belongs to Cardiovascular; Trimethoprim belongs to Anti Bacterial.
Why it happens
Trimethoprim amiloride-like inhibition of distal sodium channels combined with ARB-induced aldosterone suppression decreases potassium excretion.
What to do
Avoid the combination in patients with renal impairment or other hyperkalemia risks and use an alternative antibiotic when possible. If used, check serum potassium and creatinine within several days of starting.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Olmesartan and Trimethoprim, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
Other interactions of Olmesartan
- Aliskiren + Olmesartan Contraindicated
- Olmesartan + Sparsentan Contraindicated
- Aldesleukin + Olmesartan Major
- Amifostine + Olmesartan Major
- Amiloride + Olmesartan Major
- Amlodipine-benazepril + Olmesartan Major
Other interactions of Trimethoprim
Frequently asked questions
Can I take Olmesartan with Trimethoprim?
MediHelp rates the interaction as major. 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 lowers aldosterone effect. Together they can cause marked hyperkalemia, especially in older patients or those with renal impairment.
How serious is the interaction between 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: Avoid the combination in patients with renal impairment or other hyperkalemia risks and use an alternative antibiotic when possible. If used, check serum potassium and creatinine within several days of starting.
What other medicines interact with Olmesartan?
MediHelp also lists interactions of Olmesartan with, for example, Aliskiren, Sparsentan, Aldesleukin. The full list is on the Olmesartan page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
