Longitudinal patterns of benzodiazepine consumption in a German cohort of methadone maintenance treatment patients
Objective: Cross-sectional studies show that considerable proportions of opiate dependents in methadone maintenance treatment (MMT) consume benzodiazepines (BZD). The longitudinal patterns of BZD use over time were described here. Methods: After admission to MMT, patients from two outpatient MMT clinics (n=345) were observed for up to 2years whilst in treatment. The use of BZD, cannabis, opiates and cocaine was assessed by urine sampling carried out twice a month. Results: For the whole sample, the mean BZD-positive urine specimen rate was 0.36 during the first 3months. Rates slightly decreased during the first year and remained stable afterwards (last observation carried forward). For study completers (n=152), the rate decreased over time, from 0.31 (first 3-month period) to 0.19 (last period; p < 0.001). According to a longitudinal cluster analysis, 26% of all patients showed a pattern of constantly high BZD-positivity rates, mostly in combination with other substances. Inpatient detoxifications from BZD (carried out in 18% of cases) did not have a sustained effect on levels of BZD use. Conclusions: BZD consumption in MMT is often part of a polydrug consumption pattern and is associated with poorer treatment retention. It is necessary to further investigate the reasons for BZD use in MMT patients and to develop effective interventions to reduce levels of BZD consumption.