Generic
Prazosin Hydrochloride
18 brands available in the market
At a glance
Prazosin Hydrochloride is an alpha-blocker used for the treatment of hypertension, left ventricular failure, Raynaud's phenomenon, and benign prostatic hyperplasia. It lowers blood pressure by blocking postsynaptic α1-adrenoceptors, causing vasodilation.
Description
Prazosin decreases total peripheral vascular resistance through selective inhibition of postsynaptic α1-adrenoceptors in vascular smooth muscle. Blood pressure is lowered in both supine and standing positions; this effect is more pronounced on diastolic blood pressure. Rebound elevation of blood pressure does not occur following abrupt cessation.
Indications
- Hypertension (primary and secondary)
- Left ventricular failure
- Raynaud's phenomenon and Raynaud's disease
- Benign prostatic hyperplasia (BPH)
Therapeutic class
Alpha adrenoceptor blocking drugs
Pharmacological class
α1-Adrenoceptor Antagonist
Pharmacology
Prazosin blocks postsynaptic α1-adrenoceptors in vascular smooth muscle, decreasing total peripheral vascular resistance. It lowers blood pressure, reduces left ventricular filling pressure, and increases cardiac output. In prostatic and urethral smooth muscle, it improves BPH symptoms by blocking α1-receptors.
Mechanism of action
Lowers blood pressure by blocking α1-adrenoceptors, causing vasodilation.
Dosage
Adult Dose (Oral):
- Hypertension: Initial 0.5 mg 2-3 times daily (3-7 days); 1 mg 2-3 times daily (next 3-7 days); maintenance up to 15 mg/day in divided doses; max 20 mg/day
- BPH: Initial 0.5 mg twice daily; maintenance up to 2 mg twice daily
- Raynaud's: 1-5 mg every 12 hours
- Elderly and hepatic impairment: Dose reduction needed
- XR tablet: 2.5 mg once daily initially; gradually increase to 20 mg/day
Administration
- May be taken with or without food; take at a fixed time
- Swallow tablet whole; do not chew, crush, or break
- XR tablet must be swallowed whole; do not bite or divide
Missed dose
If you miss a dose, take it as soon as you remember; skip if it's almost time for next dose; do not double the dose.
Side effects
Common Side Effects:
- Dizziness
- Headache
- Drowsiness
- Lack of energy
- Weakness
- Palpitations
- Nausea
- Orthostatic hypotension
Precautions & warnings
- May affect driving ability; do not drive if drowsy or dizzy
- Risk of postural hypotension with first dose; start with low dose
- Avoid alcohol (may enhance hypotensive effect)
- Inform doctor before cataract surgery
- Caution in pregnancy and lactation
Contraindications
- Known sensitivity to quinazolines
- Congestive heart failure due to mechanical obstruction
- Pregnancy
Drug interactions
- Diuretics, other antihypertensives: Enhanced hypotensive effect
- β-blockers, calcium channel blockers: Increased risk of first-dose hypotension
- PDE5 inhibitors (sildenafil): Additive hypotensive effect
Food interactions
Alcohol with Prazosin may cause excessive drowsiness.
Use in pregnancy
Use in Pregnancy: May be unsafe during pregnancy; animal studies have shown harmful effects; consult your doctor.
Pregnancy Category: C — always consult a doctor before taking during pregnancy.
Use in lactation
Use in Lactation: Probably unsafe; excreted in small amounts in human milk; caution required.
Pediatric use
Not recommended for children under 12 years.
Geriatric use
Elderly patients require dose reduction; blood pressure monitoring required.
Renal / hepatic impairment
Renal Impairment: Safe in kidney disease; dose adjustment may not be needed; start with low dose; consult your doctor.
Hepatic Impairment: Caution in liver disease; dose reduction needed; consult your doctor.
Overdose effects
Overdose (≥50 mg): Profound drowsiness, depressed reflexes; if hypotension occurs, place patient supine, volume expanders, vasopressors if needed; prazosin is not dialyzable (protein-bound).
Storage conditions
Keep away from light and moisture, store below 30°C; keep out of reach of children.
Chemical structure
Prazosin Hydrochloride