Promoting abstinence from cocaine and heroin with a methadone dose increase and a novel contingency

Abstract

To test whether a combination of contingency management and methadone dose increase would promote abstinence from heroin and cocaine, we conducted a randomized controlled trial using a 2 × 3 (dose × contingency) factorial design in which dose assignment was double-blind. Participants were 252 heroin- and cocaine-abusing outpatients on methadone maintenance. They were randomly assigned to methadone dose (70 or 100 mg/day, double-blind) and voucher condition (noncontingent, contingent on cocaine-negative urines, or “split”). The “split” contingency was a novel contingency that reinforced abstinence from either drug while doubly reinforcing simultaneous abstinence from both: the total value of incentives was “split” between drugs to contain costs. The main outcome measures were percentages of urine specimens negative for heroin, cocaine, and both simultaneously; these were monitored during a 5-week baseline of standard treatment (to determine study eligibility), a 12-week intervention, and a 10-week maintenance phase (to examine intervention effects in return-to-baseline conditions). DSM-IV criteria for ongoing drug dependence were assessed at study exit. Urine-screen results showed that the methadone dose increase reduced heroin use but not cocaine use. The split 100 mg group was the only group to achieve a longer duration of simultaneous negatives than its same-dose noncontingent control group. The frequency of DSM-IV opiate and cocaine dependence diagnoses decreased in the active intervention groups. For a split contingency to promote simultaneous abstinence from cocaine and heroin, a relatively high dose of methadone appears necessary but not sufficient; an increase in overall incentive amount may also be required.

Introduction

Opiate-dependent patients in methadone-maintenance programs often abuse both heroin and cocaine (ONDCP, 2004). Ongoing abuse of either drug can be effectively decreased with contingency management (CM), in which a desired behavior is monitored (e.g. by frequent urine testing for drug use) and reinforced (e.g. by vouchers with monetary value). However, CM is less effective when targeted toward multiple drugs simultaneously (Peachey, 1987, Griffith et al., 2000, Prendergast et al., 2006).

Accordingly, some attempts to target CM toward heroin and cocaine simultaneously have had negative or only modest results. When methadone-maintained patients were offered $1155 in vouchers for heroin and cocaine abstinence over 12 weeks, most never earned a voucher (Downey et al., 2000). In a similar study in an outpatient drug-free program, with $1087 in vouchers available, the rate of drug-free urines was only 20%, with no significant difference between the CM condition and a control condition (Katz et al., 2002). Another study tested a stepwise approach in which the initial requirement was abstinence from cocaine and heroin, then from all illicit drugs for a possible $755 in vouchers over 16 weeks. The effect of CM was small (almost 50% of CM patients never provided a negative specimen), slow to develop (significant differences during treatment weeks 12–16 only), and dissipated immediately upon cessation of the contingency (Piotrowski et al., 1999).

A few studies targeting dual drug contingencies have yielded positive results, but only in the context of an intensive psychosocial intervention (Silverman et al., 2001), in the absence of a control group (Katz et al., 2001), or with high-magnitude vouchers ($3369 over 9 weeks) (Dallery et al., 2001). The last finding supports the argument that voucher-based CM can almost always be efficacious, but does little to address concerns about its cost. (See Section 4 for other relevant studies.) Although widespread implementation of voucher-based CM may be hindered as much by philosophical objections as by cost concerns (Kirby et al., 2006), cost is nonetheless worth addressing.

In the present study, we explored a new way to target interventions toward cocaine and heroin use simultaneously without increasing the overall cost of the vouchers beyond that typically used in studies of this type (e.g. $1155 in vouchers for 12 weeks of abstinence from a targeted drug—note that this refers to the maximum amount available, not to the amount that every participant will earn). We were also interested in continuing a previous line of research in which we systematically assessed the interaction between methadone dose and voucher incentive effects (Preston et al., 2000), using a higher range of doses than we had previously tested.

In a between-subjects, 2 × 3 design, we tested the interaction between methadone dose (70 mg/day vs. 100 mg/day) and two abstinence incentive strategies, with a noncontingent-voucher condition serving as control. The first strategy was to target all voucher earnings on cocaine. Our rationale was that this would allocate all available voucher resources toward a problem for which there is no pharmacological intervention, while taking full advantage of the effectiveness of methadone for heroin use: higher doses of methadone are associated with lower rates of heroin use (Strain et al., 1993, Ling et al., 1996, Schottenfeld et al., 1997). It also seemed possible that reinforcement of cocaine abstinence would generalize to increases in heroin abstinence (Silverman et al., 1998). However, such “carryover” of effects is not seen consistently, and may be most reliable when methadone doses are lower than those in the present study (Epstein and Preston, 2008). The second, novel strategy was to split the contingent earnings and across the two drugs of interest (heroin and cocaine) and offer half the amount for abstinence from each drug independent of abstinence from the other drug. Thus, a participant who had used one drug would still have an incentive to abstain from the other drug before the next clinic visit. We hypothesized that through this mechanism, the “split contingency” would increase abstinence from each drug, and, on the general principle that “abstinence begets abstinence” (Higgins et al., 2000a, Kirshenbaum et al., 2009), would ultimately increase the frequency of simultaneous abstinence from both drugs without costing more than a contingency aimed at one drug alone. We also hypothesized that this effect would be more prominent when abstinence from illicit opiates was facilitated by the use of a higher dose of methadone.