What is the recommended adult dosing regimen of prazosin for hypertension and for PTSD‑related nightmares, including titration schedule and maximum dose?

Prazosin Adult Dosing

For hypertension, start prazosin at 1 mg at bedtime and titrate gradually to typical maintenance doses of 2-6 mg daily; for PTSD-related nightmares, start at 1 mg at bedtime and titrate by 1-2 mg every few days, with civilians typically requiring 3-4 mg/day and military veterans often needing 9.5-15.6 mg/day. 1, 2

Initial Dosing Strategy

Always begin with 1 mg at bedtime regardless of indication to minimize the risk of first-dose hypotension and syncope. 1, 2 This conservative starting approach is critical—clinical experience with 22,000 patients showed syncope occurred in 1 of every 667 patients (0.15%) when this 1 mg initial dose was used. 3

Key First-Dose Precautions:

• Monitor blood pressure after the initial dose and with each significant dose increase 1, 2
• Consider withholding diuretics for 1 day before initiating therapy if treating hypertension 3
• Use lower initial doses in elderly patients or those on concurrent antihypertensive medications 1

Titration Schedule

Increase by 1-2 mg every few days until clinical response is achieved. 1, 2 The titration should be gradual and guided by both therapeutic response and blood pressure tolerance.

Target Doses by Indication

For PTSD-Related Nightmares:

Civilian populations:

• Average effective dose: 3-4 mg/day (mean 3.1 ± 1.3 mg) 1, 2
• Optimal doses in civilian trauma studies ranged from 1-4 mg/day 4
• Give as a single bedtime dose initially 1

Military veteran populations:

• Require substantially higher doses: 9.5-15.6 mg/day 1, 2
• Gender differences exist: men require mean effective dose of 15.6 ± 6.0 mg, while women require 7.0 ± 3.5 mg 1
• Studies of military patients have used doses of 10-16 mg at night 5
• Consider divided dosing for more severe cases, especially in military personnel 1

For Hypertension:

• Maintenance doses typically 2-6 mg daily 5
• Can be used alone or in combination therapy 3
• Fluid retention may develop on long-term therapy and may necessitate adding a diuretic 3

Maximum Doses

While no absolute maximum is specified in guidelines, the evidence shows:

• Civilian PTSD patients rarely need more than 4 mg/day 1, 4
• Military veterans with PTSD may require up to 15-16 mg/day 1, 5
• Doses above 5 mg were associated with marked improvement in combat trauma nightmares 6

Monitoring Requirements

• Blood pressure monitoring is essential after initial dose and with each increase 1, 2
• Assess nightmare frequency and intensity using standardized measures when treating PTSD 1
• Watch for orthostatic hypotension, especially in elderly or those on antihypertensives 2, 7

Common Pitfalls to Avoid

Do not use prazosin as a general anxiolytic—it is specifically indicated for trauma-related nightmares, not general anxiety disorders. 2 It works by reducing CNS sympathetic outflow and only reduces anxiety symptoms if they stem from trauma-related nightmares causing sleep deprivation. 2

Be aware of SSRI interactions—concurrent SSRI use may diminish prazosin's response in PTSD patients. 1, 2

Expect symptom return upon discontinuation—nightmares typically return to baseline intensity if prazosin is stopped, as this is not a curative treatment. 1, 2

Side Effect Management

• Dizziness and lightheadedness are common, especially after initial doses 1
• Transient orthostatic hypotension may occur but usually resolves during treatment 1
• Side effects are usually mild and transient, seldom requiring discontinuation 3
• Sexual dysfunction is uncommon 3

Special Population Considerations

Patients with baseline low blood pressure or high fall risk should be carefully evaluated before starting prazosin, as orthostatic hypotension is the most frequently reported adverse event requiring monitoring. 7