Drug interactions
Chlorthalidone + Trimethoprim
Severity: Moderate
Chlorthalidone and Trimethoprim: moderate 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
Thiazide-type diuretics and trimethoprim can each lower serum sodium, so combined use may increase the risk of hyponatremia, especially in older adults. Trimethoprim may also raise potassium, though chlorthalidone partly counteracts this.
What this interaction means in plain words
Chlorthalidone and Trimethoprim can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Chlorthalidone belongs to Cardiovascular; Trimethoprim belongs to Anti Bacterial.
Why it happens
Additive renal sodium loss from thiazide-type diuresis and trimethoprim's blockade of distal epithelial sodium channels.
What to do
Check serum sodium and potassium within the first week of combined use, especially in elderly patients, and stop or change therapy if significant hyponatremia occurs.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Chlorthalidone
Other interactions of Trimethoprim
Frequently asked questions
Can I take Chlorthalidone with Trimethoprim?
MediHelp rates the interaction as moderate. Chlorthalidone and Trimethoprim can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Thiazide-type diuretics and trimethoprim can each lower serum sodium, so combined use may increase the risk of hyponatremia, especially in older adults. Trimethoprim may also raise potassium, though chlorthalidone partly counteracts this.
How serious is the interaction between Chlorthalidone and Trimethoprim?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Check serum sodium and potassium within the first week of combined use, especially in elderly patients, and stop or change therapy if significant hyponatremia occurs.
What other medicines interact with Chlorthalidone?
MediHelp also lists interactions of Chlorthalidone with, for example, Amifostine, Atenolol-chlorthalidone, Candesartan-hydrochlorothiazide. The full list is on the Chlorthalidone page.
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