An interim analysis was done on the first 190 patients who completed the study and found a significant effect on relapse prevention of the naltrexone implant as compared to oral and placebo naltrexone, with corresponding risk reduction in HIV risk injection practices. There was a slight trend for oral naltrexone vs. placebo for relapse prevention, but unlike our earlier studies, it was not significant. We think that the apparent loss of efficacy for oral naltrexone is because the patients are now older and it is more difficult to enlist their mothers and other close relatives in supervising adherence. These preliminary findings were presented at the 2009 CPDD meeting in Reno, NV.