Employment-based reinforcement of adherence to depot naltrexone in unemployed opioid-dependent adults: a randomized controlled trial

Abstract

Aims: Naltrexone can be used to treat opioid dependence, but patients refuse to take it. Extended-release depot formulations may improve adherence, but long-term adherence rates to depot naltrexone are not known. This study determined long-term rates of adherence to depot naltrexone and whether employment-based reinforcement can improve adherence.

Design: Participants who were inducted onto oral naltrexone were assigned randomly to contingency (n = 18) or prescription (n = 17) groups. Participants were offered six depot naltrexone injections and invited to work at the therapeutic workplace on week days for 26 weeks, where they earned stipends for participating in job skills training. Contingency participants were required to accept naltrexone injections to maintain workplace access and to maintain maximum pay. Prescription participants could work independently of whether they accepted injections.

Setting: The therapeutic workplace, a model employment-based intervention for drug addiction and unemployment.

Participants: Opioid-dependent unemployed adults.

Measurements: Depot naltrexone injections accepted and opiate-negative urine samples.

Findings: Contingency participants accepted significantly more naltrexone injections than prescription participants (81% versus 42%), and were more likely to accept all injections (66% versus 35%). At monthly assessments (with missing urine samples imputed as positive), the groups provided similar percentages of samples negative for opiates (74% versus 62%) and for cocaine (56% versus 54%). Opiate-positive samples were more likely when samples were also positive for cocaine.

Conclusions: Employment-based reinforcement can maintain adherence to depot naltrexone. Future research should determine whether persistent cocaine use compromises naltrexone's effect on opiate use. Workplaces may be useful for promoting sustained adherence to depot naltrexone.

Conflict of interest statement

Conflict of Interest: The other authors report no conflicts of interest or financial disclosures.

© 2011 The Authors, Addiction © 2011 Society for the Study of Addiction.

Figures

Figure 1

The flow of participants through the study.

Figure 2

The percentage of depot naltrexone injections accepted by participants in the Prescription and Contingency Groups. Bars show group percentages and circles show individual percentages. Open circles show individuals for whom depot naltrexone treatment was discontinued for medical reasons.

Figure 3

The percentage of participants retained in depot naltrexone treatment (continued to take scheduled depot naltrexone injections; top panel) and the therapeutic workplace (continued attending the workplace; bottom panel) across study weeks.

Figure 4

Naltrexone blockade and opiate and cocaine urinalysis results across consecutive trice weekly urine samples collected when participants attended the therapeutic workplace. Within each panel, rows of data represent the results for individual participants. Urinalysis results are based on samples collected three times per week, typically on Monday, Wednesday and Friday of each week. Samples prior to the left of the vertical black line at 0 on the horizontal axis were collected prior to random assignment while participants were taking oral naltrexone. Black squares indicate urine samples negative for both opiates and cocaine; orange squares indicate opiate positive urine samples; white squares with crosses indicate cocaine positive urine samples; orange squares with crosses indicate samples positive for both opiates and cocaine. Empty sections indicate missing samples. Shaded portions show when participants were blocked by naltrexone (i.e., the sample was collected within 3 weeks of the last naltrexone injection). Vertical lines after urine samples 0, 9, 18, 27, 36, and 45 indicate the time of scheduled injections. Within each panel, participants are arranged from top to bottom from those with the most to least naltrexone blockade, most to least opiate negative samples, and then most to least cocaine negative samples.