Hydrochlorothiazide

Hydrochlorothiazide, sold under the brand name Hydrodiuril among others, is a diuretic medication used to treat hypertension and swelling due to fluid build-up. Other uses include treating diabetes insipidus and renal tubular acidosis and to decrease the risk of kidney stones in those with a high calcium level in the urine. Hydrochlorothiazide is taken by mouth and may be combined with other blood pressure medications as a single pill to increase effectiveness. Hydrochlorothiazide is a thiazide medication which inhibits reabsorption of sodium and chloride ions from the distal convoluted tubules of the kidneys, causing a natriuresis. This initially increases urine volume and lowers blood volume. It is believed to reduce peripheral vascular resistance.

Potential side effects include poor kidney function, electrolyte imbalances, including low blood potassium, and, less commonly, low blood sodium, gout, high blood sugar, and feeling lightheaded with standing.

Two companies, Merck & Co. and Ciba Specialty Chemicals, state they discovered the medication which became commercially available in 1959. It is on the World Health Organization's List of Essential Medicines. It is available as a generic drug and is relatively affordable. In 2021, it was the twelfth most commonly prescribed medication in the United States, with more than 39 million prescriptions.