The purpose of the study is to evaluate if the drug prazosin:

• will decrease alcohol use in active duty members of the military who served in Iraq and/or Afghanistan and
• determine if presence or absence of posttraumatic stress disorder affects treatment.

The proposed study is a 19-week, titration to stable dose, randomized, two-group parallel-design, double-blind, placebo-controlled trial to evaluate the efficacy of prazosin for decreasing alcohol use in 200 active duty Service Members who served in the conflicts in Iraq and/or Afghanistan who are receiving standard outpatient treatment for alcohol use disorders at Joint Base Lewis-McChord. Treatment groups will be stratified by presence or absence of posttraumatic stress disorder (PTSD) and by assignment to the 6-week or 12-week Army Substance Abuse Program. The hypotheses are that: 1) prazosin is more effective than placebo for alcohol use disorders in these Service Members; and 2) that prazosin effect size will be greater in Service Members with PTSD than without PTSD.

Inclusion Criteria

• Male and female active duty returnees from the conflicts in Iraq and/or Afghanistan over the age of 21 with a current Diagnostic and Statistical Manual of Mental Disorders IV diagnosis of Alcohol Abuse or Dependence or a current Diagnostic and Statistical Manual of Mental Disorders 5 diagnosis of Alcohol Use Disorder
• Participant in Army Substance Abuse Program (6 or 12 week program)
• Recent alcohol consumption: more than 14 (women) or 21 (men) drinks per week for at least 2 weeks in the past 60 day period OR at least 2 days of heavy drinking in the past 60 day period (4 or more drinks for women and 5 or more drinks for men)
• Good general medical health (see Exclusion Criteria below)
• Women of childbearing potential must agree to abstain from sexual relations that could result in pregnancy or use an effective method of birth control acceptable to both participant and the study clinician during the study. Men are not required to use contraception during the study.
• Concomitant use of naltrexone and/or antabuse must be stable for 2 weeks prior to Baseline
• Capacity to provide informed consent
• English fluency

Exclusion Criteria

• Current diagnosis of opioid, methamphetamine, cocaine, marijuana, or other illegal substance dependence or abuse.
• Signs or symptoms of alcohol withdrawal at the time of initial consent
• Current diagnosis of schizophrenia, other psychotic disorder, manic phase of bipolar disorder, or cognitive disorder.
• Suicide attempt or suicidal ideation with intent in the past month.
• Significant acute or chronic medical illness, including unstable angina, recent myocardial infarction, history of congestive heart failure, preexisting hypotension (systolic <100) or orthostatic hypotension (defined as a systolic drop > 20 mmHg after two minutes standing accompanied by lightheadedness or syncope); insulin-dependent diabetes mellitus; chronic renal or hepatic failure, acute pancreatitis, Meniere's disease. Liver function tests more than 5 times the upper limit.
• Concomitant use of trazodone (due to increased risk of priapism). There will be a two week trazodone washout period before the baseline visit.
• Concomitant use of an alpha-1 blocker medication or insulin
• Use of prazosin in the 4 weeks prior to Baseline.
• History of prazosin sensitivity/allergy