Drug interactions
Triamterene + Trimethoprim
Severity: Major
Triamterene 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
Both drugs block the epithelial sodium channel in the distal nephron, reducing potassium excretion. Together they can cause severe hyperkalemia, particularly in older patients or those with renal impairment. Triamterene may also raise trimethoprim levels and cause renal dysfunction.
What this interaction means in plain words
Triamterene 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.
Triamterene belongs to Cardiovascular; Trimethoprim belongs to Anti Bacterial.
Why it happens
Additive epithelial sodium channel blockade in the distal nephron reducing urinary potassium excretion.
What to do
Avoid if possible and choose a different antibiotic; if used, monitor serum potassium and creatinine within a few 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?
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Other interactions of Triamterene
- Amiloride + Triamterene Contraindicated
- Eplerenone + Triamterene Contraindicated
- Potassium citrate / citric acid + Triamterene Contraindicated
- Potassium citrate + Triamterene Contraindicated
- Spironolactone + Triamterene Contraindicated
- Aceclofenac + Triamterene Major
Other interactions of Trimethoprim
Frequently asked questions
Can I take Triamterene with Trimethoprim?
MediHelp rates the interaction as major. Triamterene 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. Both drugs block the epithelial sodium channel in the distal nephron, reducing potassium excretion. Together they can cause severe hyperkalemia, particularly in older patients or those with renal impairment. Triamterene may also raise trimethoprim levels and cause renal dysfunction.
How serious is the interaction between Triamterene 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 if possible and choose a different antibiotic; if used, monitor serum potassium and creatinine within a few days of starting.
What other medicines interact with Triamterene?
MediHelp also lists interactions of Triamterene with, for example, Amiloride, Eplerenone, Potassium citrate / citric acid. The full list is on the Triamterene page.
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