Opioid addiction is a chronic disorder (1
) that can persist throughout a lifetime (2
). Many patients relapse after treatment (5
), suggesting that opioid addiction may require ongoing treatment. Methadone is an effective opioid agonist treatment medication (7
), particularly when used for long-term maintenance (8
). However, because of its agonist effects, methadone is highly regulated; its availability is restricted; it is illegal in some countries; its use is often discouraged (e.g., by employers); and many opioid-dependent individuals simply do not want agonist treatment (7
). Antagonist treatments may be useful alternatives.
Naltrexone is an antagonist that blocks the reinforcing, subjective, and physiological effects of opioids (9
). Because naltrexone is nonaddicting and without agonist effects, there is no risk of abuse and it is subject to little regulation. Despite these attributes, the utility of naltrexone treatment has been limited because most opioid-dependent individuals refuse it (13
). Clinicians and researchers throughout the world have been interested in promoting effective use of naltrexone (15
Oral naltrexone can require daily dosing, which may limit adherence. Extended-release depot formulations have been developed to reduce the frequency of dosing and improve adherence (14
). Depot naltrexone is safe and effective in blocking opioid effects for several weeks (17
). The depot formulation could be an ideal means of delivering naltrexone as a maintenance intervention, although we do not know whether individuals will maintain its use over extended periods of time.
If naltrexone is to be used as a maintenance intervention, effective means might be needed to promote its long-term use. Behavioral interventions hold promise for enhancing adherence to naltrexone treatment (19
). Adherence to oral naltrexone treatment can be promoted through explicit reinforcement of naltrexone ingestion (20
). Given the positive results with oral naltrexone, reinforcement might also be effective in promoting adherence to depot naltrexone. However, practical means of administering and financing long-duration reinforcement of naltrexone use are needed.
Workplaces have features that could make them ideal vehicles for administering and financing reinforcement of naltrexone use (24
). First, individuals maintain regular and extended contact with their places of employment, which could facilitate long-duration treatment. Second, wages could be used to reinforce naltrexone ingestion, which could facilitate the financing of the intervention. Third, through Employee Assistance Programs, workplaces have become common and accepted providers of substance abuse services. Finally, workplaces are everywhere, a feature that could facilitate the dissemination of employment-based reinforcement of depot naltrexone acceptance.
Recent clinical trials have shown that workplaces can be used to reinforce therapeutic behavior change in drug-addicted adults (25
). In these studies, unemployed drug abuse patients were hired and paid as employees in a model therapeutic workplace. To gain access to the workplace and maintain maximum earnings, patients were required to provide routine evidence of recent drug abstinence. The therapeutic workplace intervention has been effective at initiating and maintaining abstinence from opiates and cocaine for as long as three years (26
The present study assessed long-term rates of adherence to depot naltrexone and determined if employment-based reinforcement could increase acceptance of depot naltrexone injections. Unemployed opioid-dependent adults who completed an opioid detoxification and who were inducted onto oral naltrexone were invited to attend the therapeutic workplace for six months, randomly assigned to one of two groups, and prescribed one depot naltrexone injection every three weeks for 15 weeks. Contingency group participants were required to accept the injections to attend the workplace and to maintain maximum earnings. Prescription group participants could access the workplace independent of whether they accepted injections. We expected that Contingency participants would accept more naltrexone injections than Prescription participants.