What is the dosing of Prazosin (an alpha-1 adrenergic receptor antagonist) for the treatment of nightmares associated with Post-Traumatic Stress Disorder (PTSD)?

From the Guidelines

Prazosin should be started at a low dose of 1 mg at bedtime for treating nightmares, with gradual increases by 1 mg every few days as needed and tolerated, up to a maximum of 20 mg, as evidenced by the most recent and highest quality study 1. The dosing of prazosin for nightmares, particularly those associated with PTSD, is crucial for effective symptom control while minimizing side effects.

• The dose can be increased to between 3-15 mg at bedtime for most patients, with some requiring up to 20 mg for optimal benefit.
• It is essential to start with a low dose to reduce initial side effects like dizziness, lightheadedness, and first-dose orthostatic hypotension, as noted in the study 1.
• Taking the first dose at bedtime while lying down can help mitigate these side effects.
• Blood pressure monitoring is necessary, especially during dose adjustments, due to prazosin's mechanism as an alpha-1 adrenergic antagonist originally developed as an antihypertensive medication.
• The medication works by blocking the effects of norepinephrine in the brain, believed to be overactive during nightmares, particularly in PTSD, as supported by the evidence 1.
• Improvement in nightmares may be noticed within days to weeks of reaching an effective dose.
• The medication should be continued as long as it remains effective and well-tolerated, with periodic reassessment of the need for ongoing treatment, considering the potential interaction with antidepressant medications 1.

From the Research

Prazosin Dosing for Nightmares

• The efficacy of prazosin for the treatment of posttraumatic stress disorder (PTSD)-related nightmares has been reviewed in several studies 2, 3, 4.
• Prazosin dosages as low as 1 mg daily have been shown to be effective in reducing nightmares in patients with PTSD 2.
• The prazosin dose ranged from 1 to 16 mg/d in various studies, with mixed results for the reduction of nightmares 3.
• A therapeutic benefit of prazosin occurred within one week of initiation, with suppression of nightmare symptoms 2.
• The most frequently reported adverse event was orthostatic hypotension 2.

Studies on Prazosin for Nightmares

• A systematic review of 21 studies, including 4 randomized controlled trials (RCTs), found that prazosin was effective in reducing nightmares in patients with PTSD 3.
• A review of the literature found that prazosin demonstrated favorable clinical efficacy and was safe for relieving PTSD-associated nightmares 4.
• A case report found that prazosin was effective in managing nightmares in a patient with metastatic breast cancer who did not meet diagnostic criteria for PTSD 5.
• A narrative review found that evidence of varying quality exists for the use of prazosin in the treatment of post-traumatic nightmares (PTNs) 6.

Effective Dosing and Administration

• Prazosin has been shown to be effective in reducing nightmares at dosages as low as 1 mg daily 2.
• The optimal dosing and administration of prazosin for nightmares is not well established and may require further study 3, 4.
• Prazosin may be initiated alongside interdisciplinary psychosocial support to manage nightmares in patients with serious illness 5.