Cocaine abstinence during methadone maintenance: effects of repeated brief exposure to voucher-based reinforcement

This study determined whether abstinence engendered by intermittent reinforcement might generalize to nonreinforced periods and enhance overall rates of cocaine abstinence among methadone maintenance patients. Participants were randomized to 1 of 3 groups. The quantitative group (n = 14) earned incentives for a 50% decrease in urine benzoylecgonine concentrations; the qualitative group (n = 13) earned incentives for providing urines with concentrations <300 ng/ml. Both reinforced groups received 12 random opportunities to earn 100 US dollars in vouchers for abstinence. The control group (n = 15) was encouraged to abstain on 12 occasions under the same schedule. Incentive participants achieved significantly more cocaine abstinence on earning than on nonearning days, with no difference between quantitative and qualitative groups. The study supports brief abstinence test efficacy but did not find that unpredictable opportunities to earn incentives generalized to nonreinforced days.