a doubleblind placebocontrolled study of the opiate antagonist naltrexone in the treatment of pathological gambling urges objective pathological gambling pg is a disabling disorder experienced by approximately 1 of adults and for which few empirically validated treatments exist this study examined the efficacy and tolerability of the opioid antagonist naltrexone in adults with pg who have urges to gamblemethod an 18week doubleblind placebocontrolled trial was conducted to evaluate the safety and efficacy of 3 doses of oral naltrexone for pg seventyseven individuals with dsmivtr pg were randomly assigned to naltrexone 50 mgday 100 mgday or 150 mgday or placebo subjects were assessed with the pathological gambling adaptation of the yalebrown obsessive compulsive scale pgybocs the urge and behavior subscales of the pgybocs the gambling symptom assessment scale gsas the clinical global impressionsseverity of illness scale cgis and measures of depression anxiety and psychosocial functioning data were collected from september 2002 to june 2005results outcomes did not significantly differ between the various doses of naltrexone subjects assigned to naltrexone had significantly greater reductions in pgybocs total scores p 0094 gambling urges p 0053 and gambling behavior p 0134 compared to subjects assigned to placebo subjects assigned to naltrexone also had greater improvement in overall gambling severity reflected in the cgis scores p 0080 and in psychosocial functioning p 0177 than subjects assigned to placebo a complete analysis n 49 demonstrated significantly greater improvement on all variables for subjects assigned to naltrexone a sex analysis demonstrated that men and women did not differ significantly in their response to naltrexoneconclusion subjects assigned to naltrexone demonstrated statistically significant reductions in gambling urges and behavior in pg lowdose naltrexone 50 mgday appeared as efficacious as higher doses 100 mgday and 150 mgday and all doses were well tolerated