Benign prostatic hyperplasia (off-label for symptom relief)
Pheochromocytoma-induced hypertension (adjunct)
Dosage
Hypertension (adults): 1 mg orally 2–3 times daily initially; titrate gradually to 10 mg/day as tolerated
BPH (off-label): 1 mg orally 2–3 times daily; adjust based on symptom relief
Special considerations: Start with low dose at bedtime to minimize first-dose hypotension
Note: Monitor blood pressure and heart rate; adjust dose cautiously in elderly patients.
Route of Administration
Oral (capsule or tablet)
Mechanism of Action
Prazosin selectively blocks alpha-1 adrenergic receptors on vascular smooth muscle, causing vasodilation and reducing peripheral vascular resistance, which lowers blood pressure. It also relaxes smooth muscle in the bladder neck and prostate.
Common Adverse Effects
Dizziness
Headache
Orthostatic hypotension
Fatigue
Nasal congestion
Serious Adverse Effects
Severe hypotension or syncope (especially with first dose)
Palpitations
Priapism (rare)
Contraindications
Hypersensitivity to prazosin
Severe hypotension
Precautions
Monitor blood pressure, especially after first dose
Use caution in elderly patients and those on other antihypertensives
Rise slowly from sitting or lying position to avoid dizziness
Drug Interactions
Other antihypertensives – additive hypotensive effect
Use with caution; consult healthcare provider. Limited data in pregnancy; monitor blood pressure closely. Use during breastfeeding only if clearly needed.
Patient Counseling
Take first dose at bedtime to reduce risk of dizziness/fainting
Rise slowly from sitting or lying positions
Monitor blood pressure regularly
Report severe dizziness, fainting, or prolonged erections