Methadone Maintenance Treatment in New Zealand

Introduction Methadone maintenance treatment (MMT) is an effective treatment for individuals with established opioid dependence. However, reviews of the literature reveal that MMT is not a standardised treatment, client outcomes vary and consumer ambivalence is common. In the international literature there has been an increasing emphasis on evaluating client outcomes during treatment and clients’ treatment perceptions. This programme of research focused on an examination of MMT in respect to client sociodemographic characteristics, substance use, injecting risk, health and wellbeing and treatment perceptions as well as MMT characteristics. Further assessments of the properties of the Degree of Drug Use Index (DDI), a brief measure of substance use, were also conducted. Method The cross-sectional longitudinal follow-up investigations were conducted with representative samples of Māori and non-Māori clients (established on MMT) recruited from the Christchurch Methadone Treatment Programme (MTP). Of the 107 participants at baseline, 93 were followed up, on average, 23 months later. To investigate test-retest reliability of the DDI, a further 80 participants were systematically recruited from the Christchurch MTP waiting list. Seventy-three participants completed a retest interview after a mean of 7.1 days. In addition, a small staff sample (n=10) from a range of MTP settings offered to trial the DDI and provide structured feedback. Results The profile of the MMT client sample was that almost a quarter were over 40 years of age, one in five (primarily women) were full time parents, less than one quarter were employed and over half were receiving a sickness or invalid benefit. Compared to SF-36 population norms the MMT participants, on average, reported significantly poorer health and wellbeing. In contrast to national results there were no significant ethnicity or gender differences. Poorer social functioning and mental health were associated with higher frequency of benzodiazepine use. More women than men reported taking medication for a mental health problem and women reported significantly higher frequency of benzodiazepine use than men. Paired comparisons showed a significant reduction in injecting drug use and follow-up and a high reported opioid abstinence rate as well as a significant overall reduction in benzodiazepine use. Rates of nicotine and cannabis use were virtually unchanged. Over half of those who reported injecting drug use at follow-up reported sharing injecting equipment. While the average methadone dose was within the therapeutic range, nearly a third considered that their dose was inadequate. During the course of these investigations one woman died and, of those who completed follow-up, 10 non-Māori withdrew from methadone. At follow-up four of these 10 participants had not been readmitted to treatment, were living in the community and reported no recent opioid use. The range of responses on the Treatment Perceptions Questionnaire (TPQ) included some strongly negative ratings. Employed participants scored significantly higher than unemployed participants. Higher SF-36 scores for general health, social functioning and mental health and participant selfratings of treatment progress were significantly positively associated with TPQ scores. Higher methadone doses and frequency of benzodiazepine use were significantly associated with lower scores. Māori participants rated their treatment progress significantly lower than non-Māori. DDI assessments showed that this brief measure met feasibility and psychometric requirements for outcome instruments for routine clinical use. Conclusions Overall, the findings from these investigations support the general effectiveness of MMT in reducing illicit opioid use and injecting drug use within the context of continuous treatment and therapeutic methadone doses. However, they also show variations in substance use and health related outcomes, including some ethnicity and gender differences, as well as variations in client perceptions. Key clinical implications arise from these finding as well as important areas for further investigation.