thiazide thiazide thiazide (/ˈθaɪəzaɪd/) refers to both a class of sulfur-containing organic molecules and a class of diuretics based on the chemical structure of benzothiadiazine. the thiazide drug class was discovered and developed at merck and co. in the 1950s. the first approved drug of this class, chlorothiazide, was marketed under the trade name diuril beginning in 1958. in most countries, thiazides are the least expensive antihypertensive drugs available. thiazidedrug classchlorothiazide, the first thiazide drugclass identifiersusehypertension, edemaatc codec03abiological targetsodium-chloride symporter