What is the recommended dosing of prazosin for treating nightmares in patients with Post-Traumatic Stress Disorder (PTSD)?

Prazosin Dosing for PTSD-Associated Nightmares

Start prazosin at 1 mg at bedtime and titrate by 1-2 mg every few days until nightmares are adequately controlled, with typical effective doses of 3-4 mg/day for civilians and 9.5-15.6 mg/day for military veterans. 1, 2

Initial Dosing Strategy

• Begin with 1 mg at bedtime to minimize the risk of first-dose orthostatic hypotension 1, 2
• Monitor blood pressure after the initial dose and with each significant dose increase 2, 3
• Use lower starting doses in elderly patients or those taking concurrent antihypertensive medications 2

Titration Protocol

• Increase by 1-2 mg every few days based on clinical response and tolerability 1, 2
• Assess nightmare frequency and intensity at each titration step using standardized measures when possible 2
• Continue titration until nightmares are adequately suppressed or side effects limit further increases 1

Target Dose Ranges by Population

The effective dose varies substantially based on the patient population:

Civilian Trauma Victims

• Average effective dose: 3-4 mg/day (mean 3.1 ± 1.3 mg) 1, 2, 4
• Dose range: 1-10 mg/day 1
• Treatment response typically occurs within 3-9 weeks 1

Military Veterans

• Average effective dose: 9.5-15.6 mg/day 1, 2, 4
• Veterans often require substantially higher doses than civilians 2, 4
• Some treatment-resistant cases may benefit from doses up to 20-30 mg/day, though this exceeds typical guideline recommendations 5, 6

Gender Considerations in Active-Duty Military

• Men: mean effective dose 15.6 ± 6.0 mg/day 2
• Women: mean effective dose 7.0 ± 3.5 mg/day 2

Administration Schedule

• Give as a single bedtime dose for initial management 2, 3
• For severe cases, particularly in military personnel requiring higher doses, divided dosing may be considered (e.g., larger dose at bedtime with smaller midmorning dose) 2, 6

Monitoring and Safety

Blood Pressure Monitoring

• Check blood pressure after the first dose and with each significant increase 2, 3
• Orthostatic hypotension is the most common side effect, though usually transient and resolves during treatment 1, 3
• Dizziness and lightheadedness are common, especially after initial doses 2, 3

Drug Interactions

• SSRIs may diminish prazosin's response in PTSD patients, so consider this interaction when planning treatment 2, 3
• Patients maintained their ongoing psychotherapy and psychotropic medications during clinical trials without significant issues 1

Clinical Pitfalls and Caveats

Common Mistakes to Avoid

• Don't stop at low doses prematurely: Many clinicians hesitate to increase prazosin due to side effect concerns, but military veterans often need 9.5-15.6 mg/day for adequate response 2, 4, 5
• Don't use prazosin as a general anxiolytic: It's specifically indicated for trauma-related nightmares, not generalized anxiety 3
• The American Academy of Sleep Medicine frames prazosin as treatment for nightmare disorder with secondary benefits on PTSD symptoms 3

Treatment Expectations

• Nightmares return to baseline if prazosin is discontinued, so this is not a curative treatment 2, 3
• Therapeutic benefit can occur within one week of initiation, though studies evaluated 3-9 weeks of treatment 1, 7
• Prazosin was generally well tolerated across all studies, with orthostatic hypotension being the primary limiting side effect 1

Evidence Quality

The American Academy of Sleep Medicine provides a Level A recommendation for prazosin in PTSD-associated nightmares based on three Level 1 placebo-controlled trials involving 98 patients 1, 3. All three studies demonstrated statistically significant reductions in trauma-related nightmares versus placebo, with CAPS Item No. 2 scores improving from 4.8-6.9 at baseline to 3.2-3.6 after treatment 1.