Prazosin Dosing for PTSD-Related Nightmares
For PTSD-related nightmares, prazosin should be started at 1 mg at bedtime and gradually increased by 1-2 mg every few days until clinical response, with effective doses typically ranging from 3-4 mg for civilians and 9.5-15.6 mg for military veterans. 1, 2
Initial Dosing and Titration
- Start with 1 mg at bedtime to minimize risk of first-dose hypotension 1, 2
- Increase by 1-2 mg every few days until clinical response is achieved 1, 2
- Lower initial doses should be used in elderly patients or those on concurrent antihypertensive medications 2
- Clinical response may begin within one week of prazosin initiation 3
Population-Specific Effective Dose Ranges
- Civilians with PTSD-related nightmares: Average effective dose is approximately 3-4 mg/day 1, 2
- Military veterans with PTSD-related nightmares: Higher doses are often required, with mean effective doses ranging from 9.5-15.6 mg/day 1, 2
- Gender differences in active-duty military personnel: Men may require higher doses (mean 15.6 ± 6.0 mg) compared to women (mean 7.0 ± 3.5 mg) 2
- Some treatment-resistant cases may require doses up to 20-45 mg daily, though these higher doses are less common and should be approached cautiously 4, 5
Administration Schedule
- Initially administer as a single bedtime dose for nightmare management 2
- For more severe cases, especially in military personnel, divided dosing may be considered (bedtime and mid-morning) 2, 5
- Maximum recommended dosage is 20 mg at bedtime with potential addition of 5 mg mid-morning for severe cases 5
Monitoring and Considerations
- Monitor blood pressure after initial dose and with each significant dose increase due to risk of orthostatic hypotension 2, 3
- Be aware that patients taking selective serotonin reuptake inhibitors (SSRIs) may have a diminished response to prazosin 1, 2
- Prazosin is effective in both civilian and military populations, including older adults with chronic PTSD 2, 6
- Discontinuation may lead to return of nightmares to baseline intensity 2, 7
Common Side Effects
- Dizziness and lightheadedness are common, especially after initial doses 2
- Orthostatic hypotension may occur but usually resolves during continued treatment 2, 3
- Despite these potential side effects, prazosin is generally well-tolerated, even in older adults 3, 6
Mechanism of Action
- Prazosin is an alpha-1 adrenergic receptor antagonist that reduces CNS sympathetic outflow 1, 7
- Norepinephrine plays an important role in the pathophysiology of PTSD-related nightmares, and prazosin helps reduce elevated CNS noradrenergic activity 1
While prazosin has shown efficacy in multiple studies, it's worth noting that a recent large trial showed contradictory results, particularly in patients concurrently taking antidepressants 1. However, the American Academy of Sleep Medicine still suggests prazosin as the most established medication for PTSD-related nightmares 7.