The opioid antagonist nalmefene significantly reduces urges and behaviors associated with pathological gambling compared with placebo, according to an article in the February issue of the American Journal of Psychiatry.

The four-month trial led by Jon E. Grant, MD, JD, included 207 participants at 15 US outpatient treatment centers. Three doses of nalmefene -- 25, 50, and 100 mg/day were compared with placebo.

The proportion of patients who were rated as “much improved” or “very much improved” at their last evaluation was significantly higher in the group taking 25 mg/day of nalmefene (59 percent) than in the placebo group (34 percent).

Both the 25 mg/day and 50 mg/day groups demonstrated significant reductions in gambling urges, thoughts, and behavior. The 25 mg group had the lowest dropout rate of the three nalmefene groups; however, the rates for the drug groups were not significantly higher than that of the placebo group. Liver function remained normal.
“The study is part of emerging evidence that gambling, once thought to be a problem in moral integrity, is instead a problem in brain biology and can be treated successfully,” said Robert Freedman, MD, journal editor-in-chief.

Pathological gambling is estimated to affect one percent of the population. Various psychosocial treatments are in use, but few medications have been consistently superior to placebo for pathological gambling.

The findings add to the growing evidence for the involvement of brain neurochemicals in addictive behaviors, such as gambling. Nalmefene blocks opioid receptors. Dopamine increases gambling. Increased dopamine resulting from treatment of Parkinson’s disease by L-dopa and other drugs can cause some elderly Parkinson’s patients to become pathological gamblers for the first time in their lives.

The Food and Drug Administration has not yet approved the oral form of nalmefene for general clinical use in the USA.