Starting Dose of Prazosin for PTSD
Begin prazosin at 1 mg at bedtime for PTSD-associated nightmares, then increase by 1-2 mg every few days until clinical response is achieved. 1, 2, 3
Initial Dosing Protocol
- Always start with 1 mg at bedtime to minimize the risk of first-dose syncope and orthostatic hypotension 1, 2, 3
- The FDA label explicitly warns that patients should always be started on 1 mg capsules, and the 2 mg and 5 mg capsules are not indicated for initial therapy 3
- Monitor blood pressure within 30-90 minutes after the first dose, as syncopal episodes most commonly occur during this window 3
Titration Strategy
- Increase by 1-2 mg every few days based on clinical response and tolerability 1, 2
- The gradual titration minimizes the approximately 1% risk of syncope that occurs with initial doses of 2 mg or greater 3
- Continue titration until nightmares and sleep disturbances improve adequately 1
Target Maintenance Doses
The effective dose varies significantly by population:
- Civilian trauma victims: Average effective dose is 3-4 mg/day (range 1-4 mg), with a mean of 3.1 ± 1.3 mg 1, 2, 4
- Military veterans: Require substantially higher doses, with mean effective doses of 9.5-15.6 mg/day 1, 2, 5
- Gender differences in active-duty personnel: Men require mean doses of 15.6 ± 6.0 mg, while women require 7.0 ± 3.5 mg 2
Critical Monitoring Points
- Check orthostatic blood pressure after the initial dose and with each significant dose increase 2
- Watch for dizziness and lightheadedness, especially in elderly patients or those on concurrent antihypertensive medications 1, 2
- Lower initial doses are necessary if the patient is taking other antihypertensives or beta-blockers, as additive hypotensive effects can occur 3
Common Pitfalls to Avoid
- Do not start with 2 mg or higher doses despite the FDA-approved hypertension dosing of 1 mg two to three times daily—PTSD dosing is different and uses bedtime-only administration initially 3
- Do not underdose military veterans—they typically need 9.5-15.6 mg/day, not the 3-4 mg that works for civilians 1, 2
- Be aware of SSRI interactions—concurrent SSRI use may diminish prazosin's response in PTSD patients 2, 6
- Recognize that nightmares return to baseline if discontinued—this is symptomatic treatment, not curative 2, 6
Advanced Dosing Considerations
- For patients with breakthrough daytime flashbacks or symptoms, consider divided dosing (twice or three times daily) rather than single bedtime dosing 7
- Some treatment-resistant cases may require doses up to 30-45 mg daily, though this is far beyond typical ranges 8
- The short 2-3 hour half-life of prazosin means that once-daily dosing may lead to breakthrough symptoms between doses in some patients 7