SUSTAINED COCAINE ABSTINENCE, IN METHADONE-MAINTENANCE PATIENTS THROUGH VOUCHER-BASED REINFORCEMENT THERAPY

Background: Chronic cocaine abuse remains a serious and costly public health problem. This study assessed the effectiveness of a voucher-bas ed reinforcement contingency in producing sustained cocaine abstinence . Methods: A randomized controlled trial compared voucher-based reinfo rcement of cocaine abstinence to noncontingent voucher presentation. P atients were selected from 52 consecutively admitted injecting heroin abusers in a methadone maintenance treatment program. Patients with he avy cocaine use during baseline period (N=37) participated. Except whe re otherwise indicated, the term cocaine abuse is used in this article in a generic sense and not according to the DSM-III-R definition. Pat ients exposed to abstinence reinforcement received a voucher for each cocaine-free urine sample (ie, negative for benzoylecgonine) provided three times per week throughout a 12-week period; the vouchers had mon etary values that increased as the number of consecutive cocaine-free urine samples increased. Control patients received noncontingent vouch ers that were matched in pattern and amount to the vouchers received b y patients in the abstinence reinforcement group. Results: Patients re ceiving vouchers for cocaine-free urine samples achieved significantly more weeks of cocaine abstinence (P=.007) and significantly longer du rations of sustained cocaine abstinence (P=.001) than controls. Nine p atients (47%) receiving vouchers for cocaine-free urine samples achiev ed between 7 and 12 weeks of sustained cocaine abstinence; only one co ntrol patient (6%) achieved more than 2 weeks of sustained abstinence. Among patients receiving vouchers for cocaine-free urine samples, tho se who achieved sustained abstinence (greater than or equal to 5 weeks ) had significantly lower concentrations of benzoylecgonine in baselin e urine samples than those who did not achieve sustained abstinence (P less than or equal to.01). Patients receiving voucher reinforcement r ated the overall treatment quality significantly higher than controls (P=.002). Conclusion: Voucher-based reinforcement contingencies can pr oduce sustained cocaine abstinence in injecting polydrug abusers.