Drug interactions
Captopril-hydrochlorothiazide + Trimethoprim
Severity: Major
Captopril-hydrochlorothiazide and Trimethoprim: major interaction.
Last updated Sources: US FDA label
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 sodium channels in the distal nephron and reduces potassium excretion, and captopril lowers aldosterone. Together they can cause clinically significant hyperkalemia, especially in older patients or those with renal impairment; hydrochlorothiazide only partly offsets this.
What this interaction means in plain words
Captopril-hydrochlorothiazide 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.
Captopril-hydrochlorothiazide belongs to Cardiovascular; Trimethoprim belongs to Anti Bacterial.
Why it happens
Additive reduction in renal potassium excretion from ENaC blockade by trimethoprim and decreased aldosterone with ACE inhibition.
What to do
Check serum potassium and creatinine within several days of starting trimethoprim and avoid the combination in renal impairment if possible. Use an alternative antibiotic when feasible.
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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References
Other interactions of Captopril-hydrochlorothiazide
- Aliskiren + Captopril-hydrochlorothiazide Contraindicated
- Captopril-hydrochlorothiazide + Dofetilide Contraindicated
- Captopril-hydrochlorothiazide + Sacubitril / valsartan Contraindicated
- Aceclofenac + Captopril-hydrochlorothiazide Major
- Aldesleukin + Captopril-hydrochlorothiazide Major
- Amifostine + Captopril-hydrochlorothiazide Major
Other interactions of Trimethoprim
Frequently asked questions
Can I take Captopril-hydrochlorothiazide with Trimethoprim?
MediHelp rates the interaction as major. Captopril-hydrochlorothiazide 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 sodium channels in the distal nephron and reduces potassium excretion, and captopril lowers aldosterone. Together they can cause clinically significant hyperkalemia, especially in older patients or those with renal impairment; hydrochlorothiazide only partly offsets this.
How serious is the interaction between Captopril-hydrochlorothiazide 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: Check serum potassium and creatinine within several days of starting trimethoprim and avoid the combination in renal impairment if possible. Use an alternative antibiotic when feasible.
What other medicines interact with Captopril-hydrochlorothiazide?
MediHelp also lists interactions of Captopril-hydrochlorothiazide with, for example, Aliskiren, Dofetilide, Sacubitril / valsartan. The full list is on the Captopril-hydrochlorothiazide page.
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