Hydrochlorothiazide
Hydrochlorothiazide, sometimes abbreviated HCT, HCTZ, or HZT is a popular diuretic drug that acts by inhibiting the kidneys' ability to retain water. This reduces the volume of the blood, decreasing blood return to the heart and thus cardiac output and, by other mechanisms, is believed to lower peripheral vascular resistance. Hydrochlorothiazide is sold both as a generic drug and under a large number of brand names, including: Apo-Hydro, Aquazide H, Dichlotride, Hydrodiuril, HydroSaluric, Microzide, Oretic.

Activity
Hydrochlorothiazide belongs to the thiazide class of diuretics, acting on the kidneys to reduce sodium (Na) reabsorption in the distal convoluted tubule. This reduces the osmotic pressure in the kidneys, causing less water to be reabsorbed by the collecting ducts. This leads to increased urinary output.

Indications
HCT is often used in the treatment of hypertension, congestive heart failure, symptomatic edema and the prevention of kidney stones. It is effective for nephrogenic diabetes insipidus (paradoxical effect, which decreases urine formation) and is also sometimes used for hypercalciuria and Dent's Disease.

Hypokalemia, an occasional side-effect, can be usually prevented by potassium supplements or combining hydrochlorothiazide with a potassium-sparing diuretic.

Side effects
Hypokalemia
Hypomagnesemia
Hyperuricemia and gout
High blood sugar
High cholesterol
Headache
Impotence
Nausea/vomiting
NOTE: This list needs references. The NIH link provided below does not agree with several items on this list.