A drug used to treat urinary problems caused by an enlarged prostate. It is also used to treat high blood pressure and is being studied in the treatment of other conditions. Terazosin hydrochloride relaxes muscle tissue in blood vessels and in the prostate. It is a type of alpha blocker.

The hydrochloride salt form of terazosin, a quinazoline derivative with adrenergic antagonistic property. Terazosin hydrochloride selectively inhibits alpha-1 adrenergic receptors, resulting in vasodilation leading to decreased peripheral vascular resistance and a reduced venous return to the heart as well as decreased urethral resistance, which potentially improving urine flow and symptoms related to benign prostatic hyperplasia. In addition, terazosin decreases low-density lipoproteins (LDL) and triglycerides while increasing the concentration of high-density lipoproteins (HDL).