Terazosin

• Benign prostatic hyperplasia (BPH) - enlarged prostate
• Hypertension (high blood pressure)
• Urinary retention related to BPH
• Combination therapy for resistant hypertension
• Kidney stones (off-label, to help pass stones)

Terazosin is an alpha-1 adrenergic receptor blocker used to treat benign prostatic hyperplasia (BPH) and hypertension. It works by relaxing smooth muscle in the prostate and blood vessels, improving urinary flow and lowering blood pressure.

How Terazosin Works

Terazosin selectively blocks alpha-1 adrenergic receptors in the prostate, bladder neck, and blood vessels. In BPH, this relaxation of prostatic smooth muscle reduces urethral resistance, improving urine flow without affecting prostate size. In hypertension, vasodilation reduces peripheral vascular resistance and blood pressure.

Pharmacokinetics

Terazosin is well absorbed after oral administration with bioavailability near 90%. Peak plasma levels occur within 1-2 hours. The medication has a relatively long half-life of 12 hours, allowing once-daily dosing. It is extensively metabolized in the liver.

Medical Uses

Terazosin is FDA-approved for treating BPH symptoms (urinary hesitancy, weak stream, frequency, urgency) and hypertension. It may be preferred when a patient has both conditions. Some studies suggest alpha-blockers may reduce progression of BPH symptoms.

Dosing Information

Treatment typically starts with 1 mg at bedtime to minimize first-dose hypotension. The dose is gradually increased at weekly intervals to 2 mg, then 5 mg, and up to 10-20 mg daily based on response. For BPH, most patients respond to 10 mg daily.

First-Dose Effect

Terazosin can cause significant first-dose hypotension, particularly orthostatic hypotension with dizziness and syncope. The first dose should be given at bedtime, and patients should be cautioned about getting up slowly. Similar precautions apply when restarting after missed doses or increasing the dose.

Important Safety Information

Common side effects include dizziness, fatigue, headache, and nasal congestion. Terazosin may cause intraoperative floppy iris syndrome (IFIS) during cataract surgery. Patients should inform their ophthalmologist about alpha-blocker use before eye surgery.

Drug Interactions

Terazosin can enhance the hypotensive effects of other blood pressure medications, particularly other alpha-blockers. Caution is needed when combining with phosphodiesterase-5 inhibitors (sildenafil, tadalafil) due to additive hypotensive effects. NSAIDs may reduce the antihypertensive effect.

Comparison with Other Alpha-Blockers

Compared to tamsulosin and alfuzosin, terazosin is less selective for prostate tissue (alpha-1A receptors) and more likely to cause cardiovascular effects. However, this makes it useful for patients who also need blood pressure reduction. It is generally less expensive than newer agents.

Special Populations

Elderly patients are more susceptible to orthostatic hypotension and should use caution. Dose adjustment is not typically required for renal impairment. Use during pregnancy should only occur if clearly needed, as effects on fetal development are unknown.

Learn more at MedlinePlus