Ace Inhibitor and Trimethoprim: Drug Interaction Guide

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

Interaction severity: Moderate — caution required

How Ace Inhibitor interacts with Trimethoprim

Trimethoprim blocks epithelial sodium channels in the distal nephron (amiloride-like effect), reducing potassium excretion; combined with ACE inhibitor it can cause severe hyperkalaemia.

What you should do

Check serum potassium and renal function before and 3-5 days into therapy, especially in elderly or renal impairment. Consider alternative antibiotic.

Key facts

Severity

Moderate — caution required

Mechanism

Trimethoprim blocks epithelial sodium channels in the distal nephron (amiloride-like effect), reducing potassium excreti...

Action

Check serum potassium and renal function before and 3-5 days into therapy, especially in elderly or renal impairment. Co...

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 Ace Inhibitor and Trimethoprim together?

With caution. Check serum potassium and renal function before and 3-5 days into therapy, especially in elderly or renal impairment. Consider alternative antibiotic.

What is the severity of this interaction?

The interaction between Ace Inhibitor and Trimethoprim is classified as Moderate — caution required. Trimethoprim blocks epithelial sodium channels in the distal nephron (amiloride-like effect), reducing potassium excretion; combined with ACE inhibitor it can cause severe hyperkalaemia.

What should I do if I'm prescribed both?

Check serum potassium and renal function before and 3-5 days into therapy, especially in elderly or renal impairment. Consider alternative antibiotic. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

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