Improvement in naltrexone treatment compliance with contingency management

Abstract

The efficacy of a voucher-based incentive program for improving adherence to outpatient, thrice weekly naltrexone maintenance was tested in a three group, randomized, 12-week clinical trial. Voucher incentives were given as follows: contingent group (n=19) for each consecutive naltrexone dose ingested; non-contingent group (n=19) on unpredictable schedule independently of taking naltrexone; no-voucher group (n=20) none. Vouchers were exchangeable for goods and services. The contingent group had significantly longer treatment retention and ingested significantly more doses of naltrexone (consecutive and total) than either control group. Voucher incentives can significantly increase adherence to naltrexone maintenance in recently detoxified opioid dependent individuals.

Introduction

Heroin dependence is a significant medical and social problem (Nurco et al., 1985, Cherubin and Sapira, 1993). Although opioid agonist maintenance with methadone or LAAM is an effective treatment of opioid dependence, it is not universally available for many individuals who could benefit from treatment (Institute of Medicine, 1995). In particular, opioid agonist maintenance may not be appropriate for individuals who abuse opioids but are not physically dependent, and those who have been dependent for less than one year do not qualify under the current federal regulations. Nevertheless, these patients may be at significant risk for developing medical problems such as HIV and hepatitis infection (Vlahov et al., 1991, Gossop et al., 1993, Thomas et al., 1995). A potential alternative treatment is opioid antagonist maintenance with naltrexone.

Naltrexone is a long-acting competitive opioid antagonist that holds promise as an effective pharmacotherapy for opioid abuse. Taken regularly in adequate doses, naltrexone can block the reinforcing effects of opioids and markedly diminish or eliminate opioid self-administration, discrimination, and self-reported mood effects (Martin et al., 1973, Harrigan and Downs, 1978, Mello et al., 1981; Gonzalez and Brogden, 1988). Naltrexone is well tolerated and has little or no agonist effects at therapeutic doses. Most importantly, evaluations of naltrexone as a treatment agent have shown that it can be effective in reducing opioid use in patients who remain in treatment (Gonzalez and Brogden, 1988, Shufman et al., 1994). In addition, due to naltrexone’s relative lack of agonist effects, it is not scheduled under the Controlled Substances Act and is not a likely target for diversion, as is the case with opioid agonists such as methadone. As such, naltrexone is one of the few pharmacologic treatments for prevention of relapse to opioid use available without special licensing or registration requirements. By many standards naltrexone is an ideal treatment agent for opioid abuse. However, naltrexone’s utility in the treatment of opioid abuse has been severely limited as a result of one critical shortcoming: a large proportion of opioid abusers refuse to begin or continue in naltrexone treatment.

The treatment evaluations to date demonstrate clearly that only a portion of opioid abusers accept naltrexone treatment or continue in treatment for extended periods of time. Some evidence suggests that patients who are employed and married are more likely to remain in treatment (Greenstein et al., 1983). However, in public drug treatment programs, no more that 10–15% of patients have been willing to try naltrexone, and drop-out rates have been high (O'Brien and Woody, 1989). Although a number of efforts have been made to improve patient acceptance of naltrexone treatment, none of the methods has proven adequate. In an early study, Meyer and Mirin (1979)employed contingency management procedures to improve acceptance of naltrexone treatment. Patients in their treatment program received $1/day for ingesting their daily naltrexone dose at a local pharmacy, plus a $5 bonus for going to the pharmacy for seven consecutive days. Although the contingency management procedures appeared promising, by the end of 12 weeks of the contingency management program, almost all of the subjects in the program had dropped out of treatment. Grabowski et al. (1979)evaluated several schedules of payment (maximum $10.05/week) on compliance with naltrexone maintenance in nine patients who had selected naltrexone maintenance for treatment of their opioid dependence. They concluded that reinforcement schedules based on the number of doses ingested were more effective than a time-based schedule. Furthermore, patients receiving either type of reinforcement schedule showed better treatment compliance than a historical control group that received no incentives for naltrexone ingestion.

The purpose of the present study was to evaluate contingency management procedures designed to increase and sustain use of naltrexone in opioid abusers. In this study, as in previous studies (Grabowski et al., 1979, Meyer and Mirin, 1979), subjects received incentives for ingesting naltrexone. However, the contingencies employed in the present study differed in two important respects: reinforcers were substantially larger than those administered in the earlier studies; and the contingencies in the current study were designed to produce sustained and continuous use of naltrexone. Patients earned vouchers (exchangeable for goods or services) which increased in value as the number of consecutive ingested naltrexone doses increased. This reinforcement schedule was developed by Higgins and colleagues (1994) and has been shown to be effective in increasing cocaine and opiate abstinence when vouchers were used to reinforce drug-negative urine specimens (Higgins et al., 1994, Silverman et al., 1996a, Silverman et al., 1996b).