Naftopidil hydrochloride is primarily used in the treatment of benign prostatic hyperplasia (BPH), a condition characterized by the enlargement of the prostate gland. It functions as an alpha-1 adrenergic receptor antagonist, which helps relax the smooth muscles in the prostate and bladder neck, thereby improving urine flow and reducing symptoms such as difficulty in urination, frequent urination, and incomplete bladder emptying. Additionally, it is sometimes prescribed for managing lower urinary tract symptoms associated with BPH. Its selective action on alpha-1D receptors makes it effective with potentially fewer side effects compared to non-selective alpha-blockers.