Drug interactions
Lisinopril + Trimethoprim
Severity: Major
Lisinopril 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
Trimethoprim blocks epithelial sodium channels in the distal nephron, reducing potassium excretion, and lisinopril adds aldosterone suppression. Severe hyperkalemia has occurred, particularly in older patients, with renal impairment or with higher trimethoprim doses.
What this interaction means in plain words
Lisinopril 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.
Lisinopril belongs to Cardiovascular; Trimethoprim belongs to Anti Bacterial.
Why it happens
Additive reduction of renal potassium excretion through ENaC blockade and decreased aldosterone.
What to do
Consider an alternative antibiotic in high-risk patients; otherwise check serum potassium and creatinine within several days of starting trimethoprim.
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 Lisinopril
- Aliskiren + Lisinopril Contraindicated
- Lisinopril + Protein a column Contraindicated
- Lisinopril + Sacubitril / valsartan Contraindicated
- Lisinopril + Sacubitril-valsartan Contraindicated
- Amifostine + Lisinopril Major
- Amiloride + Lisinopril Major
Other interactions of Trimethoprim
Frequently asked questions
Can I take Lisinopril with Trimethoprim?
MediHelp rates the interaction as major. Lisinopril 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. Trimethoprim blocks epithelial sodium channels in the distal nephron, reducing potassium excretion, and lisinopril adds aldosterone suppression. Severe hyperkalemia has occurred, particularly in older patients, with renal impairment or with higher trimethoprim doses.
How serious is the interaction between Lisinopril 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: Consider an alternative antibiotic in high-risk patients; otherwise check serum potassium and creatinine within several days of starting trimethoprim.
What other medicines interact with Lisinopril?
MediHelp also lists interactions of Lisinopril with, for example, Aliskiren, Protein a column, Sacubitril / valsartan. The full list is on the Lisinopril page.
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