DRUG DESCRIPTION. DIURIL (Chlorothiazide) is a diuretic and antihypertensive. It is 6-chloro-2 H-1,2,4-benzothiadiazine7-sulfonamide 1,1-dioxide. It is a white, or practically white, crystalline powder with a molecular weight of 295.72, which is very slightly soluble in water, but readily soluble in dilute aqueous sodium hydroxide.