Background In an ongoing parallel-group double-blind placebo-controlled trial at the VA Puget Sound Health Care System, the efficacy of the alpha-1 adrenergic receptor antagonist prazosin is under evaluation for the treatment of combat-related posttraumatic stress disorder (PTSD), using the Clinician-Administered PTSD Scale (CAPS) to measure frequency and severity of PTSD symptoms. In a previous placebo-controlled crossover study (n = 10 subjects), researchers reported statistically greater improvements in the prazosin condition vs placebo in scores on two CAPS items that measure nightmares and sleep disturbance. Unpublished data from the ongoing study show similar improvement in these two individual items, but the total 17-item CAPS score itself is not significantly different between the two groups. Additionally, clinicians in the Mental Health Clinic at VA Puget Sound have observed anecdotally that subjects treated with prazosin at bedtime sometimes report a worsening of some PTSD symptoms the following afternoon. Because prazosin has a short duration of action, it was hypothesized that daytime symptoms may be perceived by the subjects as worsened as nighttime symptoms improve in those subjects treated with prazosin compared to placebo.
Study Design and Methods Subjects were randomized to either prazosin or placebo. Study instruments were administered at baseline and at 8 weeks. Scores on all 17 CAPS items were compared using independent group t-tests on 34 subjects (prazosin = 17, placebo = 17).
Results In addition to replicating the significant changes in the two CAPS items measuring nighttime symptoms (“distressing dreams” and “difficulty falling asleep”) seen in the earlier study, subjects in the prazosin arm also showed significant improvement in a third item, “physiological reactivity” (p = .047), a daytime symptom. There was no significant improvement in the prazosin group on any other item.
Conclusion These data do not suggest that any single CAPS item worsened in the prazosin group. An alternate explanation for the lack of improvement in the overall CAPS score is that improvements on the three individual items were insufficient to drive an improvement in the total score of all 17 CAPS items in a sample of this size. However, differences in the total CAPS score of the magnitude observed here might reach significance in a larger sample.
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