Opioid antagonists for pharmacological treatment of alcohol dependence - a critical review

Alcohol dependence is a widespread psychiatric disorder. While relapse prevention therapy in alcoholism was exclusively dominated by social and psychological treatments for many years, in the last decades the benefits of pharmacological agents for the rehabilitation treatment in alcoholism have become increasingly evident. Naltrexone, an opiate receptor antagonist, blocks the pleasant and reinforcing effects of alcohol by preventing the stimulation of opioid receptors and the reduction of dopamine release in the ventral tegmental area (VTA). Clinical evidence about the effectiveness of the substance is not always consistent, but meta-analyses confirm naltrexone's effect on the risk of heavy drinking. Evidence about the abstinence-maintaining effects of the substance comes from a relatively small database and needs further investigation. The evaluation of differential effects of naltrexone depending on biological or psychological profiles, which could further enhance the effectiveness of treatments for alcohol dependence, remains a challenge. Nalmefene, another opioid antagonist, as well as naltrexone depot, a sustained release formulation of naltrexone, are further promising strategies for the treatment of alcohol dependence. The review at hand gives on overview of the current evidence on opioid antagonists for the treatment of alcohol dependence regarding the possible mechanism of action, the substances' safety profiles and their effectiveness. The corresponding evidence is critically reviewed taking into consideration the influence of the study design on the magnitude and consistency of effect sizes as well the impact of patient characteristics on the response to the treatment with opioid antagonists. Future studies on the role of different subtypes of alcoholics according to their genetic or psychological profile to explain or even predict the effects of opioid antagonists in the treatment of alcohol dependence are needed.