The generic name of the drug Terazosin is Terazosin Hydrochloride Capsules. Possible adverse effects of prolonged use include weakness, dizziness, nausea, and postural hypotension, with specific side effects varying depending on the dosage of the medication. The drug is used to treat benign prostatic hyperplasia and also to treat high blood pressure. It can be used alone or in combination with other anti-hypertensive drugs. Adverse effects may include weakness, postural hypotension, dizziness, drowsiness, nasal congestion, rhinorrhea, and impotence when taken in long-term doses of 1 to 20 mg once daily, or weakness, blurred vision, dizziness, nausea, peripheral edema, palpitations, and drowsiness when taken in doses of 1 to 40 mg once daily. This product is contraindicated in those who are allergic to terazosin. This product may cause syncope and upright hypotension, and driving or hazardous work should be avoided 12 hours after the first dose, after an increase in dose, or when restarting after interruption of therapy. This product may cause abnormal penile erection and if not promptly brought to attention it may lead to permanent erectile dysfunction (impotence). If you need to use this drug, it is recommended that you use it under the supervision of a doctor.