thiazide

Thiazide refers to a class of diuretics that act on the distal convoluted tubule of the nephron to inhibit the sodium-chloride (Na-Cl) symporter. This reduces reabsorption of sodium and chloride, promoting diuresis and a decrease in extracellular fluid. Over time, thiazides also contribute to lower peripheral vascular resistance, which helps reduce blood pressure. Thiazide-like diuretics share the same mechanism but often have longer duration of action.

Common agents include hydrochlorothiazide, chlorthalidone, indapamide, metolazone, and bendroflumethiazide. Hydrochlorothiazide is among the most widely used, while chlorthalidone and indapamide are noted for longer half-lives and sometimes greater cardiovascular protective effects in hypertension. Thiazide diuretics are commonly used as first-line or add-on therapy for hypertension and are also employed to treat edema associated with heart failure, cirrhosis, and nephrotic syndrome. They can be used in nephrogenic diabetes insipidus to reduce urine volume in some patients.

Pharmacokinetics and duration vary by agent. For example, hydrochlorothiazide has a relatively rapid onset with effects evident within hours and a shorter duration, whereas chlorthalidone and indapamide provide longer-lasting action. Efficacy tends to wane with severe renal impairment, and diuretic response is reduced at very low GFR.

Adverse effects include electrolyte disturbances such as hypokalemia and hyponatremia, hyperuricemia that can precipitate gout, and mild glucose intolerance. They can cause dehydration and photosensitivity. Thiazides are sulfonamide derivatives, so caution is advised for those with sulfa hypersensitivity. Interactions include reduced effect with NSAIDs and potential electrolyte imbalances when combined with other diuretics or potassium-wparing agents.