Terazosin is an alpha-1 adrenergic blocker used to treat high blood pressure and symptoms of benign prostatic hyperplasia (BPH), a condition in which the prostate gland becomes enlarged. It works by relaxing the muscles in the blood vessels and the prostate, which helps lower blood pressure and improve urine flow in men with BPH. Terazosin is typically taken once daily and may take several weeks to achieve full therapeutic effects. Because it can cause a significant drop in blood pressure when first starting treatment, it is often initiated at a low dose and taken at bedtime to minimize dizziness or fainting.