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Spironolactone and Trimethoprim: Drug Interaction Guide

Quick answer: This combination requires caution. Spironolactone and Trimethoprim can be used together with adjustments and monitoring.

Interaction severity: Moderate — caution required

How Spironolactone interacts with Trimethoprim

Trimethoprim blocks distal tubular sodium channels in a manner similar to amiloride, while spironolactone antagonizes aldosterone; combination produces additive hyperkalaemia particularly in older adults and CKD.

What you should do

Check potassium and creatinine within 5-7 days of starting trimethoprim; consider alternative antibiotic in elderly or those with eGFR <60.

Key facts

Severity

Moderate — caution required

Mechanism

Trimethoprim blocks distal tubular sodium channels in a manner similar to amiloride, while spironolactone antagonizes al...

Action

Check potassium and creatinine within 5-7 days of starting trimethoprim; consider alternative antibiotic in elderly or t...

Important medical disclaimer: This page provides educational information about drug interactions for general reference. It is not a substitute for professional medical advice, diagnosis, or treatment. Always discuss your specific medications with a qualified healthcare provider before starting, stopping, or changing any treatment. About our editorial team.

Frequently asked questions

Can I take Spironolactone and Trimethoprim together?

With caution. Check potassium and creatinine within 5-7 days of starting trimethoprim; consider alternative antibiotic in elderly or those with eGFR <60.

What is the severity of this interaction?

The interaction between Spironolactone and Trimethoprim is classified as Moderate — caution required. Trimethoprim blocks distal tubular sodium channels in a manner similar to amiloride, while spironolactone antagonizes aldosterone; combination produces additive hyperkalaemia particularly in older adults and CKD.

What should I do if I'm prescribed both?

Check potassium and creatinine within 5-7 days of starting trimethoprim; consider alternative antibiotic in elderly or those with eGFR <60. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

Last reviewed: by iMedic Medical Editorial Team. Our editorial process.