The study will explore the efficacy and tolerability of a regimen of NAC (2400 mg) versus placebo for the treatment of alcohol dependence.

Study 1: Relapse prevention: This is a double-blind, randomized, placebo-controlled clinical trial in which participants will receive oral NAC (2400 mg: 2x 600mg tablets twice per day) or matching placebo. Trial participants will receive either oral NAC ( dose stated above) or matching placebo for up to 4 weeks.

Study 2: Withdrawal: Trial participants will receive oral NAC (dose stated above) or matching placebo within the first 24 hours of their admission for up to 3 days.

Study 3: Participants from the relapse prevention substudy will also receive 30-minute non-invasive brain imaging session prior to and after completing the treatment regime in Study 1.

Both males and females will be recruited for the study.

Inclusion Criteria:

• Male and female patients between the ages of 18 and 65 meeting DSM-IV criteria for current alcohol use disorder (this is an exclusion for the healthy control sample)
• Able to understand and sign written informed consent
• Must have a stable residence and be able to identify an individual who could locate subject if needed
• Admitted for medical detoxification from alcohol (withdrawal study only)
• Blood alcohol concentration of 0.00 (if completing brain imaging session)
• Express a desire to achieve abstinence or to greatly reduce alcohol consumption (relapse prevention study only)

Exclusion Criteria:

• Clinically significant comorbidities or medical disease that might interfere with the evaluation of the study medication or present a safety concern.
• Pregnant women and women of childbearing potential who do not practice a medically acceptable form of birth control
• Women who are breastfeeding
• Dependence on any substance other than nicotine
• Court-mandated participation in alcohol treatment or pending incarceration (relapse prevention study only)
• Treatment/ingestion during the previous week of benzodiazepines or other sedative-hypnotic medications or history of recent chronic treatment with sedative-hypnotic medications (withdrawal study only)
• Dependence on any substance other than nicotine

The following exclusion criteria are only applicable to participants undergoing the brain imaging session:

• Extreme obesity
• Pregnant or have any reason to believe they are pregnant;
• Previous brain surgery;
• Ever employed as a machinist, a welder or a metal worker;
• Epilepsy
• Metal items such as pacemakers; aneurysm clips in the brain; metal dental implants; metallic fragments in the eye or anywhere else; insulin pump; metal implants; hearing aid or a prosthetic device.