A total of 627 alcohol-dependent patients were randomly assigned to receive either an injection of long-acting naltrexone or a placebo injection; 624 ultimately received at least one injection. In addition to an injection, all participants received low-intensity counseling consisting of 12 sessions during the six-month study, in addition to study medication. Long-acting naltrexone was associated with a reduction in heavy drinking within the first month of treatment, and this response was maintained over the six-month treatment period. In addition, long-acting naltrexone was generally well tolerated and side effects were predominantly mild and decreased over time. (The three most common side effects reported were nausea, headache and fatigue.)
The study was one of the largest trials of a medication for alcohol dependence and was conducted at 24 sites nationwide, including public, private hospitals and Veterans Administration clinics and tertiary-care medical centers. Other study authors included researchers from the medical schools at the University of Connecticut, Yale University, and Harvard University, and from Alkermes Incorporated, a biotechnology company based in Cambridge, Mass., that manufactures the long-acting naltrexone formulation (Vivitrex) used in the study.