GENERIC NAME: triamterene and hydrochlorothiazide (HCTZ) DRUG CLASS AND MECHANISM: Triamterene/hydrochlorothiazide is an oral diuretic (water pill) that is used for treating high blood pressure (hypertension) and edema (water accumulation). It is a combination of two different diuretics. The FDA approved triamterene/hydrochlorothiazide in December 1965.