Efficacy and tolerability of long-acting injectable naltrexone for alcohol dependence
Background: Since the 1970s, it has been apparent that naltrexone, in many ways, is a perfect medication. It is highly specific for opiate receptors, and it has no direct (agonist) effects of its own. The only symptoms produced by naltrexone are those that occur because of displacing opiates and opioids, as would be the case when a person is taking an opiate medication or has a high level of endogenous opioids. In this situation, naltrexone displaces the opiate and produces withdrawal symptoms. Naltrexone absolutely prevents relapse to opiate addiction. In the 1980s it was discovered that naltrexone also blocks rewarding effects of alcohol that are produced through the endogenous opioid system. Unfortunately, the oral form of naltrexone generally has had poor adherence (compliance) by patients who need it most. To be effective it requires dosing at least two to three times per week, but daily is preferable. Most heroin addicts and many alcoholics simply change their minds and stop taking the medication. In the 1970s and 1980s there were efforts to produce a depot preparation, but for various reasons the preparation was unsuccessful. It was highly viscous and had to be administered via a trocar. Recently, using new technology, three small drug manufacturers have produced separate versions of a depot form of naltrexone that can be administered via a needle in a small enough volume that is practical and acceptable to patients. Effective blood levels are obtained for 30 to 40 days after the injection. Several publications of the results of clinical trials are now available.