EVIDENCE-BASED ANSWER:
Yes. Prazosin has been shown to reduce both frequency and severity of nightmares in patients who meet diagnostic criteria for post-traumatic stress disorder (PTSD) (strength of recommendation: A, systematic review of randomized, controlled trials [RCTs]).
Patients who meet PTSD criteria show best response
A 2012 systematic review of prazosin (1-16 mg) for PTSD included 21 studies (4 RCTs, 4 open-label case series, 4 retrospective case series, and 9 case reports) with 285 patients, 85% of whom were combat veterans.1 All the studies were limited by small sample sizes and a lack of demographic diversity.
To measure prazosin’s effect on nightmares, the studies used the Clinician-Administered PTSD Scale (CAPS-B2), scored from 0 to 8, which sums the frequency of nightmares (0=none in the past week, 4=daily nightmares) and the intensity of distressing dreams (0=none, 4=incapacitating distress).
The 3 highest-quality RCTs used similar methods and included only 63 patients who met diagnostic criteria for PTSD. Each found statistically significant reductions in nightmares among patients taking prazosin compared with placebo (CAPS-B2 improvements of 3.3, 3.3, and 1.5 for prazosin vs 0.4, 0.9, and 0 for placebo; P<.05 for all comparisons).
In the fourth RCT, comprised of 50 patients, only 58% of participants met full clinical diagnostic criteria for PTSD. The primary outcome was the number of recalled nightmares, which didn’t show a statistically significant decrease in the prazosin group compared with placebo (decrease in mean weekly nightmares of 0.7 with prazosin vs an increase of 0.1 with placebo).