The proposed study will examine the efficacy of doxazosin in the treatment of PTSD and alcohol use disorder or substance use disorders.

Due to sustained military conflicts in Afghanistan and Iraq over the past decade, there are an increasing number of U.S. military personnel and Veterans returning home with posttraumatic stress disorder (PTSD) and comorbid alcohol use disorders (AUD) and substance use disorders (SUD). If left untreated, Veterans with co-occurring PTSD and substance use disorders are at increased risk for developing other mental health problems (e.g., depression, anxiety), suicidal ideation and attempts, physical health problems, reduced resiliency and military readiness, employment problems, violence, and family/relationship impairment. While mental health services are in place for U.S. service members, substantial gaps in the treatment of co-occurring PTSD and SUD exist and there is little scientific evidence available to guide the provision of care. As part of the Consortium to Alleviate PTSD (CAP), the proposed study directly addresses this critical knowledge gap by testing the efficacy of doxazosin, a long-acting and selective alpha-1 adrenergic antagonist, as compared to placebo in reducing PTSD and AUD/SUD severity among U.S. military personnel. The medication to be investigated (doxazosin) represents a novel treatment approach for PTSD and AUD/SUD. While prazosin, also an alpha-1 adrenergic antagonist, has been shown to improve sleep and nightmares in military personnel with PTSD and may help reduce substance use severity, it has a short half-life of 2-3 hours and requires multiple doses each day, which is a significant limitation. In several pilot studies, doxazosin has shown promise in significantly reducing symptoms of PTSD and AUD/SUD and, in contrast to prazosin, it requires once per day dosing which confers a significant advantage in terms of translating positive findings into routine clinical practice. In this Stage II study, the investigators will (1) employ a two-arm randomized, double-blind, between-groups experimental design that will consist of 12 weeks of treatment with doxazosin or placebo medication; (2) use standardized, repeated dependent measures to rigorously assess PTSD symptomatology and AUD/SUD severity; (3) measure impairment in associated mental and behavioral health problems (e.g., depression, anxiety, sleep, risky behaviors, family/social functioning); and (4) use functional magnetic resonance imaging (fMRI) to investigate the underlying pathophysiology of comorbid PTSD/AUD and identify prognostic indicators of treatment outcome. To achieve these aims, the investigators have assembled a multidisciplinary team of investigators with nationally-recognized expertise in combat-related PTSD, substance use disorders and neuroimaging who have successfully collaborated in the past and are uniquely qualified to implement this type of investigation. The investigators represent a collaboration of faculty at the Ralph H. Johnson Veterans Affairs (VA) Medical Center and the Medical University of South Carolina (MUSC) in Charleston, SC.

Inclusion Criteria:

1. Male or female; any race or ethnicity.
2. Served in U.S. Military - any branch or operation.
3. Subjects must be able to comprehend English.
4. Meet criteria for current (i.e., last 6 months) Substance Use Disorder (SUD) using a modified version of the MINI 7.0 (i.e., must meet DSM-5 criteria for SUD in the past 6 months instead of 12 months).
5. Meet DSM-5 criteria for current (i.e., last month) PTSD.
6. Subjects taking psychotropic medications will be required to be maintained on a stable dose for at least four weeks before treatment initiation. This is because initiation or change of medications during the course of the trial may interfere with interpretation of results.
7. Must consent to random assignment to doxazosin or placebo.
8. Must consent to complete all treatment and follow-up visits.

Exclusion Criteria:

1. Subjects meeting DSM-5 criteria for current bipolar affective disorders, as the study protocol may be therapeutically insufficient.
2. Subjects experiencing significant withdrawal symptoms, as evidence by a score of 10 or above on the Clinical Institute Withdrawal Assessment of Alcohol (CIWA). These subject will be referred for clinical detoxification and may be re-assessed for study eligibility after medically supervised detoxification has been completed.
3. Individuals considered an immediate suicide risk or who are likely to require hospitalization during the course of the study.
4. Previous treatment with doxazosin.
5. Subjects on maintenance anxiolytic, antidepressant, or mood stabilizing medications which have been initiated during the past four weeks. If it is determined, based on clinical criteria, that a subject needs to be started on maintenance medications for anxiety, mood or psychotic symptoms during the course of the study, they may be discontinued from the treatment trial.
6. Women who are pregnant, nursing or not practicing an effective form of birth control.
7. Individuals with a history of or current medical illness including unstable angina, myocardial infarction, congestive heart failure or other cardiac condition, hypotension, renal or hepatic disorders, endocrine disorders, prostate or other cancer, pancreatitis, or a seizure disorder.
8. Subjects with abnormal liver function test (LFTs) as evidenced by laboratory findings of SGOT or SGPT greater than two times normal.
9. Subjects with a history of adverse reactions to quinazolines or other alpha-1-antagonists (such as allergic reactions, priapism, hepatitis, angioedema, or intraoperative floppy iris syndrome).
10. Individuals currently taking alpha blockers (terazosin, prazosin), hypnotics/benzodiazepines, atypical antipsychotics (olanzapine, quetiapine, risperidone, clozapine), alpha-2-agonists (Clonidine, methyldopa, tizanidine, guanfacine), conivaptan, boceprevir, idelalisib, PDE-5 inhibitors or alpha-1-antagonists, protease inhibitors (treatment of HIV), oral antifungals, alfuzosin, pazopanib, silodosin, tadalafil, or tamulosin.
11. MRI exclusions: Claustrophobia; tattoos above the shoulders after evaluation by MRI technician; permanent eyeliner or permanent artificial eyebrows; cardiac pacemaker; metal fragments in eye, skin, or body, including shrapnel; heart valve replacement; brain clips; venous umbrella; being a sheet-metal worker or welder; lifetime history of aneurysm surgery; intracranial bypass, renal, or aortic clips; prosthetic devices such as middle ear, eye, joint, or penile implants; joint replacements; non-removable hearing aid, neurostimulator, or insulin pump; shunts/stents; metal mesh/coil implants; metal plate/pin/screws/wires; or any other metal implants.

Data Sharing Plan: The data collected from study participants, including PHI, will be entered into and securely stored in the STRONG STAR-CAP database on a secure UTHSCSA server by a member of the study research team under a signed Data Use Agreement between Ralph H. Johnson VA and UTHSCSA. Terms of the Data Use Agreement data have been reviewed and approved by VACO and found to meet VA security compliance standards. Electronic data will be stored, managed, and analyzed by the Data Management and Biostatistics Core staff of the STRONG STAR-CAP Consortium. The overall study PI and named collaborators will have access to identifiable data through the STRONG STAR-CAP website and UTHSCSA server.

AEs collected from baseline (if baseline lasted longer than one appointment) through follow up (12 week treatment phase and 6 week follow up - approximately 20 weeks)

Participants were asked about any changes in health or existing symptoms at each visit.