Voucher reinforcement improves medication adherence in HIV-positive methadone patients: A randomized trial

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Abstract

This clinical trial evaluated a contingency management intervention designed to improve medication adherence among HIV-positive methadone maintenance patients. After a 4-week baseline observation phase, eligible participants (N = 66) were randomly assigned to: (a) medication coaching sessions every other week to assist with adherence strategies (comparison group) or (b) medication coaching plus voucher reinforcement for opening electronic medication caps on time (voucher group). Baseline adherence (percent doses taken/percent total possible doses) was 51% using electronic measurement, 75% using self-report and 75% using pill count. The intervention was provided for 12 weeks, with a 4-week follow-up. The primary outcome results of the clinical trial indicated effectiveness during the intervention, with significant mean adherence differences between voucher and comparison groups using electronic measurement (78% versus 56%), pill count (86% versus 75%), and self-report (87% versus 69%). Differences between groups faded after vouchers were discontinued. Contingency management shows promise as a strategy to promote antiretroviral medication adherence in this population.

Introduction

Research has demonstrated that HIV-positive substance users have difficulty adhering to complex highly active antiretroviral therapy (HAART) regimens, particularly when they are actively using substances (Batki and Ferrando, 1996, Freeman et al., 1996, Fogarty et al., 2002). Cocaine use is associated with a 41% decline in median antiretroviral adherence and is a strong predictor of failure to maintain viral load (Arnsten et al., 2002). Golin et al. (2002) found that active substance and alcohol users take significantly fewer doses of HAART medication than substance-free clients. Similarly, Gebo et al. (2003) showed drug users are more than twice as likely to be non-adherent to antiretroviral regimens as non-drug users.

A considerable clinical need exists to assist substance users in taking HIV medications on time and as directed. Adherence to HAART has been associated with relative improvements in immunologic and virologic markers (Low-Beer et al., 2000, Paterson et al., 2001), increased body weight (Shikuma et al., 2004), and less rapid progression to Acquired Immunodeficiency Syndrome (AIDS; Bangsberg et al., 2001). Despite the seriousness of problems related to non-adherence, empirical studies on HAART adherence interventions for HIV-positive substance users are lacking (Simoni et al., 2005).

A significant body of work indicates that contingency management is an effective treatment for patients with substance use disorders, including those receiving methadone treatment (for example, Hall et al., 1977, Higgins et al., 1986, Calsyn et al., 1994). Voucher-based contingency management helps patients achieve and maintain abstinence from drugs by providing a voucher incentive for each drug-free urine sample. The voucher has monetary value and can be exchanged for goods and services consistent with the goals of treatment. Initially the value of the vouchers is low, but the value increases with the number of consecutive drug-free urine specimens. This approach has been successful with methadone maintenance patients in encouraging sustained abstinence from cocaine (Silverman et al., 1996a, Silverman et al., 2004) and opiates (Silverman et al., 1996b) as well as increasing full-day attendance at treatment (Jones et al., 2001).

For patients who have difficulty taking medications as directed, contingency management strategies can be used to promote adherence. Previous studies show improved isoniazid (INH) compliance with tuberculosis treatment (Elk et al., 1993, Elk et al., 1995) by dispensing methadone contingent upon INH ingestion. Similarly, Bickel et al. (1988–1989) reported on a contingency management program for alcohol-dependent patients in which continuation in methadone treatment was contingent upon daily disulfiram ingestion. Several studies have shown efficacy with opioid-dependent patients using voucher incentives to reinforce naltrexone ingestion (Carroll et al., 2001, Carroll et al., 2002, Preston et al., 1999). Contingency management may also be an efficacious intervention for substance-using HIV patients with poor HAART compliance.

The first published investigation of contingency management to improve adherence to HAART medications (Rigsby et al., 2000) was a pilot that compared three conditions: control training (i.e., encouragement), cue-dose training (i.e., identifying cues) and cue-dose training plus cash reinforcement. This randomized, controlled study (N = 55) tracked adherence using the Medication Events Monitoring System (MEMS). MEMS is an electronic monitor that registers the openings and closings of a medication bottle by using a cap containing a micro-electronic circuit. Events stored in the MEMS cap memory are transferred through a desktop communicator to a computer program that reads and stores the data, calculates results, presents visual displays, and prints reports based on patient data. In this study, reinforcement was based on one “primary” medication placed in the MEMS bottle, and patients were encouraged to cue other medications to this one. Cash reinforcement was given to participants at weekly meetings for each dose of the primary medication taken within 2 h of the prescribed dosing time. Reinforcement began at $2 per dose and increased with each consecutive dose to a maximum of $10 per day (possible earnings = $280 for 4 weeks). The reinforcement was reset to $2 if a dose was not taken within 2 h of the set dosing time. Study results demonstrated that the group receiving cue-dose training plus monetary reinforcement had significantly higher adherence during the intervention period compared to the other two groups. The mean adherence in the reinforced group increased from 70% at baseline to 88% at Week 1. The authors suggest that this rapid improvement was due to the motivating effect of reinforcement rather than new skill acquisition from cue-dose training. Four weeks of contingency management resulted in an average of 92% of doses taken on time in comparison with 70% in the non-contingency management controls. These adherence improvements were not sustained during the follow-up period, and the study did not show an effect of improved adherence on viral load. The study demonstrated the feasibility and efficacy of behavioral strategies for improving HAART adherence among HIV-positive clients using an electronic method to measure adherence.

In the present study, we adapted the use of voucher-based contingency management to reinforce taking HAART medications as prescribed. This research represents a novel application of contingency management as the first reported study to apply the use of voucher incentives to HIV medication adherence. We posited that, relative to a comparison group, participants randomly assigned to receive voucher-based contingency management would show better medication adherence (measured by MEMS cap openings, pill count, and self-report), as well as relative improvement in biological and behavioral measures of health (HIV-RNA levels, CD4+ count, and self-report).

Section snippets

Methods

The current study was a two-arm randomized controlled experiment that included a 4-week baseline phase, a 12-week intervention phase in which participants were randomized to receive or not receive voucher incentives, and a 4-week follow-up phase.

Cohort description

A total of 181 people were screened during a 31-month recruitment period. Out of those screened, 78 were ineligible. Reasons for ineligibility were: n = 7 did not have sufficient clinic records to indicate that they were HIV antibody seropositive, n = 36 were not being prescribed an antiretroviral medication for treatment of HIV/AIDS for at least 1 month, n = 9 were participating in other adherence-improvement research or clinical programs, n = 5 were living in a controlled environment that dispensed

Discussion

This study assessed whether participation in voucher reinforcement was associated with improved HIV medication adherence in methadone maintenance patients. Relative to the comparison group, participants randomly assigned to receive voucher reinforcement showed better medication adherence, measured by MEMS cap, pill count, and self-report. Differences faded after the voucher contingencies were removed. Viral load was significantly and negatively associated with the percentage of on-time MEMS cap

Acknowledgements

This project was supported by NIH Research Grants, primarily P50DA09253 (San Francisco Treatment Research Center) as well as U10DA15815, K0516752, and R01DA11344 where the medication coaching intervention was developed. The authors express gratitude to the staff and patients of the Opiate Treatment Outpatient Program (Division of Substance Abuse and Addiction Medicine, San Francisco General Hospital) and the Market Street Clinic of the Bay Area Addiction Research and Treatment Programs. We are

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