What is the recommended dosing for prazosin (Prazosin)?

Prazosin Dosing Recommendations

For adults with hypertension, prazosin should be initiated at 1 mg two or three times daily, with gradual titration to a maintenance dose of 6-15 mg daily in divided doses, not exceeding 20 mg daily. 1

Initial Dosing

• Start with 1 mg two or three times daily 1
• For patients at risk of first-dose phenomenon (especially those with recent cerebral hemorrhage), consider starting with 0.5 mg 2, 3
• Monitor blood pressure after first dose due to risk of first-dose phenomenon (sudden and severe drop in blood pressure) 1, 2

Titration

• Gradually increase dose based on blood pressure response
• Slow titration is recommended to minimize side effects
• When adding a diuretic or other antihypertensive agent, reduce prazosin dose to 1-2 mg three times daily and retitrate 1

Maintenance Dosing

• Therapeutic dosages typically range from 6-15 mg daily in divided doses 1
• Maximum recommended daily dose is 20 mg 1
• Doses higher than 20 mg usually do not increase efficacy, though some patients may benefit from further increases up to 40 mg daily in divided doses 1
• After initial titration, some patients can be maintained on a twice-daily dosage regimen 1

Special Populations

Pediatric Dosing

For children with hypertension:

• Initial dose: 0.05-0.1 mg/kg per day 4
• Maximum dose: 0.5 mg/kg per day 4
• Dosing frequency: Three times daily (TID) 4

PTSD Treatment

For treatment of PTSD-associated nightmares:

• Initial dose: 1 mg at bedtime 4, 5
• Increase by 1-2 mg every few days until effective dose is reached 4
• Maintenance dose ranges:
  • Civilian patients: Average dose ~3 mg (range 1-10 mg) 4, 5
  • Military veterans: Higher doses may be needed (9.5-15.6 mg/day) 4
  • Women may require lower doses than men (7.0 mg vs 15.6 mg in one study) 4

Important Considerations

First-Dose Phenomenon

• Risk of significant hypotension after first dose 2, 3
• Monitor blood pressure closely after initial dose
• First-dose effect may predict therapeutic response 6
• Even with recommended initial doses, severe hypotension can occur in vulnerable patients 2

Drug Interactions

• Concomitant administration with PDE-5 inhibitors can result in additive blood pressure lowering effects and symptomatic hypotension 1
• PDE-5 inhibitor therapy should be initiated at the lowest dose in patients taking prazosin 1
• Possible decreased efficacy when combined with selective serotonin reuptake inhibitors for PTSD treatment 4

Side Effects to Monitor

• Orthostatic hypotension, especially in older adults 4
• Dizziness 4
• Syncope 2

Prazosin is generally well-tolerated when properly dosed and titrated, but careful monitoring is essential, particularly after the initial dose and during dose adjustments.