A Randomized Trial of Long-Term Reinforcement of Cocaine Abstinence in Methadone-Maintained Patients Who Inject Drugs.

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Abstract
This study determined whether long-term abstinence reinforcement could maintain cocaine abstinence throughout a year long period. Patients who injected drugs and used cocaine during methadone treatment (n = 78) were randomly assigned to 1 of 2 abstinence-reinforcement groups or to a usual care control group. Participants in the 2 abstinence-reinforcement groups could earn take-home methadone doses for providing opiate- and cocaine-free urine samples; participants in 1 of those groups also could earn 5,800 US dollars in vouchers for providing cocaine-free urine samples over 52 weeks. Both abstinence-reinforcement interventions increased cocaine abstinence, but the addition of the voucher intervention resulted in the largest and most sustained abstinence. Therefore, voucher-based reinforcement of cocaine abstinence in methadone patients can be a highly effective maintenance intervention.