Hydrochlorothiazide
Hydrochlorothiazide is an established thiazide diuretic. Thiazides affect the renal tubular
mechanisms of electrolyte reabsorption, directly increasing excretion of fluid, sodium and
chloride. The diuretic action of hydrochlorothiazide reduces plasma volume, increases plasma
renin activity, increases aldosterone secretion, with consequent increases in urinary potassium
and bicarbonate loss, and decreases in serum potassium. The antihypertensive action of
hydrochlorothiazide appears to be due to combined diuretic and direct vascular activity
(reduction of vascular resistance) mechanism.