Potassium Sparing Diuretics and Trimethoprim: Drug Interaction Guide

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

Interaction severity: Major — avoid combination

How Potassium Sparing Diuretics interacts with Trimethoprim

Trimethoprim has amiloride-like epithelial sodium channel blocking activity in the distal nephron, reducing potassium excretion. Combined with potassium-sparing diuretics, this can cause severe hyperkalemia.

What you should do

Avoid when possible, especially in older adults, kidney disease, or ACE inhibitor or ARB use. If required, check potassium and renal function early and repeatedly.

Key facts

Severity

Major — avoid combination

Mechanism

Trimethoprim has amiloride-like epithelial sodium channel blocking activity in the distal nephron, reducing potassium ex...

Action

Avoid when possible, especially in older adults, kidney disease, or ACE inhibitor or ARB use. If required, check potassi...

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 Potassium Sparing Diuretics and Trimethoprim together?

No — this combination should generally be avoided. Avoid when possible, especially in older adults, kidney disease, or ACE inhibitor or ARB use. If required, check potassium and renal function early and repeatedly.

What is the severity of this interaction?

The interaction between Potassium Sparing Diuretics and Trimethoprim is classified as Major — avoid combination. Trimethoprim has amiloride-like epithelial sodium channel blocking activity in the distal nephron, reducing potassium excretion. Combined with potassium-sparing diuretics, this can cause severe hyperkalemia.

What should I do if I'm prescribed both?

Avoid when possible, especially in older adults, kidney disease, or ACE inhibitor or ARB use. If required, check potassium and renal function early and repeatedly. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

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