Literature Review - Methadone Maintenance Treatment

1. Introduction

Methadone maintenance treatment (MMT) was first introduced as a means of treating heroin withdrawal symptoms in opioid dependent persons almost forty years ago. Today, in many parts of the world, MMT is widely recognized as a key component of a comprehensive treatment and prevention strategy to address opioid dependence.¹ At the time of this review, methadone is the only opioid authorized for long-term outpatient pharmacological treatment of opioid dependence in Canada.

In Canada, as in many other countries, there is a national level regulatory framework for methadone prescription. The Office of Controlled Substances, Health Canada, works with provincial/territorial governments and medical licensing bodies to facilitate increased access to methadone maintenance treatment. To date, several provinces have developed - or are in the process of developing - guidelines and training for practitioners interested in providing methadone maintenance treatment. Although provinces have become increasingly involved in delineating the conditions under which physicians are permitted to prescribe methadone, methadone can be prescribed only by physicians who have received an exemption under the Controlled Drugs and Substances Act.

Health Canada, in collaboration with the provinces and territories, is involved in efforts to increase access to effective methadone maintenance programs.² Part of these efforts includes the production of two reports: this literature review to examine what is known about the effectiveness of methadone maintenance treatment, and a document on "best practices" in the design and delivery of methadone maintenance treatment (Health Canada, 2002a). A brochure on methadone maintenance treatment (Health Canada, 2002b), which complements the two best practices documents has also been produced. All of these documents contribute to the ongoing process of knowledge development and education for policy makers and health and social services professionals responding to the issue of opioid dependence.³

The purpose of this literature review is to provide an overview of the evidence on the effectiveness of methadone maintenance treatment. It focuses on what is known about the overall effectiveness of MMT, as well as factors that influence the effectiveness of MMT, namely:

• individual and programmatic factors,
• program development and design,
• program policies, and
• program team and environment.

Published empirical evidence on the relevant factors in MMT programs that can improve effectiveness in relation to specific populations, conditions, and settings is thin. Current literature on the specific topics of MMT and multiple substance use, women, pregnancy, comorbid medical conditions, prevention and treatment of infection with hepatitis C virus (HCV) and human immunodeficiency virus (HIV), mental health disorders, and MMT in correctional settings have been included.

This literature review is not an exhaustive review of all MMT literature, nor does it provide all the "keys" to effective delivery. Research and evaluation to fill gaps in knowledge and to improve the effectiveness of MMT is an ongoing process.

Note

In developing this document, the Investigator Team referred to sources that are believed to be reliable. This document, however, is not intended to provide readers with sufficient information to prescribe or dispense methadone.

1.1 Methodology

There is now almost forty years of accumulated research knowledge and treatment literature concerning MMT. This report relies, in large part, on comprehensive, state-of-the-art reviews of the literature that have been conducted by others. In particular, the texts edited by Ward, Mattick, and Hall (1998e), Strain and Stitzer (1999), and Lowinson, Payte, Salsitz, Joseph, Marion, and Dole (1997) have been particularly valuable. These reviews offer thorough, up-to-date reviews of current literature and practice in methadone maintenance treatment, and provide an efficient way of dealing with the huge volume of methadone maintenance treatment studies published in recent years. Although not all of the extensive numbers of primary sources cited by these texts are mentioned in this report, readers are encouraged to consult these materials.

Relevant Canadian and international literature was identified in two ways: 1) by conducting key word searches of data bases, and 2) by contacting selected experts to identify additional published or unpublished resources.

The list of databases and search terms used included:

ISI's Current Contents - Life and Social and Behavioral. Past 6 months: Subject/ Keyword Methadone Maintenance. For current literature.

• Addiction Research Foundation Library Catalogue (now a part of the Centre for Addiction and Mental Health) Subject/Keyword: Methadone Maintenance -Manuals. For practice guidelines.
• MEDLINE (Database of the National Library of Medicine, National Institutes of Health, U.S.). Several comprehensive searches, 1994 to present, limited to human, English and French. Subject/Keywords: (Methadone or Methadyl Acetate) - Therapeutic Use or Administration and Dosage combined with Methadone Maintenance in keyword or Opioid-Related Disorders (exploded) - Rehabilitation or Drug Therapy. General Search Topics: Cost Effectiveness, Administration and Dosage, Other Diseases (HIV etc.), Other Drug Use, Dual Diagnosis, Needle Exchange, Treatment Outcome, Practice Guidelines, Health Care Delivery, Accessibility, Target Populations, Drug Diversion, Mandated Treatment.
• EMBASE (Excerpta Medica) (Elsevier Science Publishers, Netherlands). Searched 1994-present. Due to overlap with MEDLINE, searched only under terms: Evidence-Based Medicine or Practice Guidelines with Methadone in Subject heading and Methadone Maintenance in keyword.
• CINAHL (Nursing and Allied Health).General Search: Methadone Maintenance, 1994-present.
• HealthSTAR (American Hospital Assoc. and National Library of Medicine. Same search terms as MEDLINE general search, 1994-. Limited to non-MEDLINE records.
• Web Sites: CCSADOCS (Database of the National Clearinghouse on Substance abuse) [www.ccsa.ca], CANBASE (Database of the Canadian Substance Abuse Information Network), NIDA (National Institute on Drug Abuse, U.S.) [www.nida.nih.gov]; CSAT (Centre for Substance Abuse Treatment); U.S; National Guideline Clearinghouse (U.S.) [www.guidelines.gov] (Agency for Health Care Policy Research, American Medical Assoc. and American Association of Health Plans); ISDD (Britain), Australian Department of Health and Aged Care.

The Canadian HIV/AIDS Clearinghouse also conducted a search of their collection for material on methadone maintenance treatment and HIV prevention.

The Investigator Team identified a vast body of literature published between 1995 and 2000, and reviewed over 300 documents for possible inclusion in the literature review. The final selection included key state-of-the-art reviews, key current reports from international and national agencies and organizations, articles presenting scientific evidence and studies or descriptions of some standard clinical practices authored by well-recognized experts in the field and published in well-recognized peer-reviewed journals or texts.

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