A number of trials have studied prazosin's effect on sleep disturbances caused by PTSD. Recent analysis of those studies by the American Society of Health-System Pharmacists found that the drug helps patients sleep longer and have fewer nightmares and awakenings. It also lessens the severity of other symptoms of PTSD, such as re-experiencing a traumatic event, avoiding certain experiences, or feeling hyper-aroused by them. Most of the clinical studies of prazosin have focused on male combat veterans. Doctors also prescribe it for female veterans and people with PTSD not related to combat, but more research is needed to determine if it's as effective for them.
In a controlled crossover trial (where each patient was given the drug and a placebo at different times), the participants, 13 nonmilitary people with PTSD, experienced fewer nightmares and sleep disturbances, plus an average of 94 minutes of increased total sleep time.
A 20-week double-blind crossover study of 10 Vietnam combat veterans and an eight-week study involving 40 veterans with chronic PTSD and severe, trauma-related nightmares tested prazosin vs. a placebo. Researchers found that the patients taking prazosin had a much higher quality of sleep, slept longer, and had fewer nightmares.
A 2010 study that compared prazosin with the antipsychotic quetiapine (Seroquel) in male combat veterans with sleep problems found the two drugs to be equally effective at six months. But those taking prazosin were more likely to have remained on it as long-term therapy, while those taking Seroquel were more likely to have stopped taking it due to adverse effects, such as gaining weight, rising cholesterol levels, the onset of type 2 diabetes, and daytime sedation.
Many experts say there should be more extensive research on prazosin, especially to determine how well it works for other patients, especially women and people with PTSD that's not related to combat. Such research could also better establish optimal dosages, how frequently a patient should take the medication, and for how long.