RETENTION RATES IN 2 NALTREXONE PROGRAMS FOR HEROIN-ADDICTS IN VITORIA, SPAIN

The main finding of a former Spanish multicenter study (SMS) on the ef fectiveness of naltrexone maintenance in heroin addicts, was the high retention rate achieved at 24 weeks of follow-up since naltrexone indu ction (40%). The authors claimed this rate was one of the highest ever reported in the literature for a non-selected sample of opiate addict s and discussed the possible relevance of a set of variables - like mo tivations and expectations due to a new treatment - on the findings. T o assess the possible effects of these variables, we have compared the retention rates in two similar naltrexone programmes. The first progr amme (hospital sample) included 56 individuals who were also included in the SMS where they accounted for 37% of the total sample. That prog ramme was developed formerly to the naltrexone marketing. The second s ample (ambulatory sample) included 67 individuals who were recruited a t least a year apart since naltrexone marketing was approved by the Sp anish Health Boards. The time-lag between the beginnig of both studies was in the range of 15 to 25 months. The subjects in both programmes had similar distributions regarding age (p = 0.27), sex (p = 0.79), we eks on treatment after naltrexone induction (p = 0.20), and program co mpliance (p = 0.78). The retention rates evaluated over a period of 24 weeks were also similar (p = 0.45). The only difference appeared at 1 2 weeks of follow-up, showing in higher retention the hospital sample than the ambulatory sample (+23%; p < 0.05). The results are discussed according to other studies and it is concluded that findings reported in the former SMS and in this study are not unusual but compatible wi th recent research. Also underlined is the potential importance of nal trexone as a concomitant treatment for extinguishing high risk behavio urs and the conditional stimuli associated with treatment relapse in h eroin addicts.