While oral naltrexone has a demonstrated ability to decrease alcohol reinforcement, it also has pharmacotherapeutic limitations, such as a small treatment effect size, adverse events, and plasma level fluctuations. The pharmacokinetic profile of naltrexone could be enhanced by intramuscular administration, which would sustain its release over several weeks and keep plasma levels relatively constant, ie, low enough to minimize side effects but high enough to reduce drinking. Vivitrex ®/Vivitrol ® and Naltrel ® are injectable naltrexone depot formulations that have been tested as possible medications for treating alcohol dependence. Their adverse-event profiles appear to be less severe than that of oral naltrexone. Vivitrex ®/Vivitrol ® has demonstrated efficacy at decreasing heavy drinking among alcohol-dependent males. Naltrel ® helped to promote abstinence and decrease the incidence of relapse in two samples of alcohol-dependent subjects. The data on a third formulation, Depotrex ®, are still limited. All three formulations require further study of their efficacy.