Drug interactions
Hydrochlorothiazide + Sulfamethoxazole
Severity: Moderate
Hydrochlorothiazide 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
Thiazide diuretics combined with sulfamethoxazole (usually given as co-trimoxazole) have been associated with hyponatremia, and thiazides have been linked with thrombocytopenia in older patients taking co-trimoxazole. Both agents can also be affected by changes in renal tubular handling, though this is of uncertain importance.
What this interaction means in plain words
Hydrochlorothiazide 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 sodium-lowering and renal effects, with possible competition for renal tubular secretion; the precise mechanism is not fully established.
What to do
Monitor serum sodium, potassium and platelet count when the combination is used, particularly in elderly patients or those with renal impairment. Stop or switch therapy if significant electrolyte disturbance or cytopenia 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 Hydrochlorothiazide
Frequently asked questions
Can I take Hydrochlorothiazide with Sulfamethoxazole?
MediHelp rates the interaction as moderate. Hydrochlorothiazide 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. Thiazide diuretics combined with sulfamethoxazole (usually given as co-trimoxazole) have been associated with hyponatremia, and thiazides have been linked with thrombocytopenia in older patients taking co-trimoxazole. Both agents can also be affected by changes in renal tubular handling, though this is of uncertain importance.
How serious is the interaction between Hydrochlorothiazide 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: Monitor serum sodium, potassium and platelet count when the combination is used, particularly in elderly patients or those with renal impairment. Stop or switch therapy if significant electrolyte disturbance or cytopenia develops.
What other medicines interact with Hydrochlorothiazide?
MediHelp also lists interactions of Hydrochlorothiazide with, for example, Dofetilide, Amifostine, Amiodarone. The full list is on the Hydrochlorothiazide page.
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