Spironolactone and Trimethoprim Sulfamethoxazole: Drug Interaction Guide

Quick answer: This is a major interaction — avoid combining Spironolactone and Trimethoprim Sulfamethoxazole unless specifically directed by your doctor.

Interaction severity: Major — avoid combination

How Spironolactone interacts with Trimethoprim Sulfamethoxazole

Trimethoprim blocks distal tubular potassium secretion (acting like amiloride) which adds to spironolactone-mediated potassium retention, causing severe hyperkalaemia especially in elderly or CKD.

What you should do

Avoid combination in elderly or patients with renal impairment, heart failure, or diabetes. If unavoidable, check potassium and creatinine within 3-5 days and use the shortest antibiotic course.

Key facts

Severity

Major — avoid combination

Mechanism

Trimethoprim blocks distal tubular potassium secretion (acting like amiloride) which adds to spironolactone-mediated pot...

Action

Avoid combination in elderly or patients with renal impairment, heart failure, or diabetes. If unavoidable, check potass...

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 Sulfamethoxazole together?

No — this combination should generally be avoided. Avoid combination in elderly or patients with renal impairment, heart failure, or diabetes. If unavoidable, check potassium and creatinine within 3-5 days and use the shortest antibiotic course.

What is the severity of this interaction?

The interaction between Spironolactone and Trimethoprim Sulfamethoxazole is classified as Major — avoid combination. Trimethoprim blocks distal tubular potassium secretion (acting like amiloride) which adds to spironolactone-mediated potassium retention, causing severe hyperkalaemia especially in elderly or CKD.

What should I do if I'm prescribed both?

Avoid combination in elderly or patients with renal impairment, heart failure, or diabetes. If unavoidable, check potassium and creatinine within 3-5 days and use the shortest antibiotic course. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

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