Drug interactions
Chlorthalidone + Sulfamethoxazole
Severity: Moderate
Chlorthalidone and Sulfamethoxazole: 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
Both thiazide-type diuretics and sulfamethoxazole-trimethoprim can lower serum sodium, so combined use may raise the risk of hyponatremia, particularly in older patients. Hyperkalemia is also possible because of the trimethoprim component, although chlorthalidone tends to offset it.
What this interaction means in plain words
Chlorthalidone and Sulfamethoxazole 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.
Why it happens
Additive effects on sodium handling: thiazide-induced renal sodium loss plus trimethoprim's amiloride-like sodium channel blockade in the distal nephron.
What to do
Check serum sodium and potassium within the first week of combined therapy, especially in elderly patients. Stop or change therapy if clinically significant hyponatremia develops.
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
Frequently asked questions
Can I take Chlorthalidone with Sulfamethoxazole?
MediHelp rates the interaction as moderate. Chlorthalidone and Sulfamethoxazole 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. Both thiazide-type diuretics and sulfamethoxazole-trimethoprim can lower serum sodium, so combined use may raise the risk of hyponatremia, particularly in older patients. Hyperkalemia is also possible because of the trimethoprim component, although chlorthalidone tends to offset it.
How serious is the interaction between Chlorthalidone and Sulfamethoxazole?
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 therapy, especially in elderly patients. Stop or change therapy if clinically significant hyponatremia develops.
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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