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May 1996

Sustained Cocaine Abstinence in Methadone Maintenance Patients Through Voucher-Based Reinforcement Therapy

Author Affiliations

From the Addiction Research Center, Intramural Research Program of the National Institute on Drug Abuse, Baltimore, Md (Drs Silverman, Montoya, Cone, Schuster, and Preston); The Johns Hopkins University School of Medicine, Baltimore (Drs Silverman, Brooner, and Preston); and University of Vermont College of Medicine, Burlington (Dr Higgins). Dr Montoya is now affiliated with L/niversitv of Antioquia, Medellin, Colombia. Dr Schuster is now affiliated with Wayne State University, Detroit, Mich.

Arch Gen Psychiatry. 1996;53(5):409-415. doi:10.1001/archpsyc.1996.01830050045007

Background:  Chronic cocaine abuse remains a serious and costly public health problem. This study assessed the effectiveness of a voucher-based reinforcement contingency in producing sustained cocaine abstinence.

Methods:  A randomized controlled trial compared voucherbased reinforcement of cocaine abstinence to noncontingent voucher presentation. Patients were selected from 52 consecutively admitted injecting heroin abusers in a methadone maintenance treatment program. Patients with heavy cocaine use during baseline period (N=37) participated. Except where otherwise indicated, the term cocaine abuse is used in this article in a generic sense and not according to the DSM-III-R definition. Patients 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 monetary values that increased as the number of consecutive cocaine-free urine samples increased. Control patients received noncontingent vouchers that were matched in pattern and amount to the vouchers received by patients in the abstinence reinforcement group.

Results:  Patients receiving vouchers for cocaine-free urine samples achieved significantly more weeks of cocaine abstinence (P=.007) and significantly longer durations of sustained cocaine abstinence (P=.001) than controls. Nine patients (47%) receiving vouchers for cocaine-free urine samples achieved between 7 and 12 weeks of sustained cocaine abstinence; only one control patient (6%) achieved more than 2 weeks of sustained abstinence. Among patients receiving vouchers for cocaine-free urine samples, those who achieved sustained abstinence (≥5 weeks) had significantly lower concentrations of benzoylecgonine in baseline urine samples than those who did not achieve sustained abstinence (P≤.01). Patients receiving voucher reinforcement rated the overall treatment quality significantly higher than controls (P=.002).

Conclusion:  Voucher-based reinforcement contingencies can produce sustained cocaine abstinence in injecting polydrug abusers.

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