Molecular Mechanisms of Opioid and Alcohol Dependence : Rationale for the Treatment by Naltrexone

Abstract

The mechanisms in opioid addiction and dependence involve cellular adaptations at several possible steps in the balance between opioid and other neurotransmitter systems in the brain. Several lines of evidence indicated that the noradrenergic system at the locus coeruleus may play pivotal role in these adaptations. The uses of opioid antagonist, naltrexone, in the treatment of opioid dependence have been widely practiced for more than 2 decades. The rationale for its efficacy in preventing relapse is strongly supported by scientific evidence, but major limitations are due to low patient compliance. The roles of psychotherapeutic methods in improving patient compliance must be emphasized in the therapeutic program. Another therapeutic indication of naltrexone is for the treatment of alcohol dependence. This theory has based on rather new evidence on the interactions between alcohol and several neurotransmitter systems, including opioid and dopa1nine. Naltrexone reverses alcohol effects on opioid receptors, dopamine release, reinforcing mechanism, euphoria, craving, and finally reduces relapse and helps patients remain abstinent for longer period of time. The use of naltrexone, thus, could be an effective therapy for alcoholism, providing that psychosocial treatment programs are fully supported.