Objective: The aim of this study was to determine the efficacy of doxazosin, an α1-adrenergic antagonist, for the treatment of co-occurring posttraumatic stress disorder (PTSD) and alcohol use disorder (AUD).
Methods: This 12-week, double-blind, randomized controlled trial of doxazosin (16 mg/d) was conducted between June 2016 and December 2019 at the Ralph H. Johnson VA Medical Center in Charleston, South Carolina. Participants were military veterans (N = 141) who met DSM-5 criteria for current PTSD and AUD and were randomly assigned to receive doxazosin (n = 70) or placebo (n = 71). Primary outcome measures were the Clinician Administered PTSD Scale (CAPS-5), the PTSD Checklist for DSM-5 (PCL-5), and the Timeline Follow-Back (TLFB).
Results: Findings from the intent-to-treat analyses revealed that participants in both groups demonstrated statistically significant reductions in CAPS-5 and PCL-5 scores (P < .0001), but, contrary to hypotheses, no significant differences were observed between groups. Percent drinking days and percent heavy drinking days also decreased significantly during treatment, but there were no differences between groups (P < .0001). Abstinence during treatment was significantly higher in the doxazosin versus the placebo group (22% vs 7%, P = .017); however, participants in the doxazosin group consumed a greater number of drinks on drinking days (6.15 vs 4.56, P = .0096). A total of 74.5% of the sample completed the treatment phase, and there were no group differences in retention or adverse events.
Conclusions: Doxazosin was safe and tolerable but was not more effective than placebo in reducing PTSD or AUD severity in this dually diagnosed sample. Clinical considerations such as heterogeneity of PTSD and AUD presentation and potential moderators are discussed in the context of future research directions.