Closure of an open drug scene--a case register-based analysis of the impact on the demand for methadone maintenance treatment.

AIMS: To assess the impact of the closure of an open drug scene on the demand for methadone maintenance treatment (MMT).

DESIGN: Interrupted time series analysis of case register-based data of all MMTs performed in the canton of Zurich (Switzerland) between June 16 1992 and July 7 1997.

SETTING: Five private and 14 state-controlled institutions as well as 330 general practitioners, 35 psychiatrists, and 79 other specialists offering outpatient MMT.

PARTICIPANTS: 5210 opiate users with 9042 MMT episodes.

MEASUREMENTS: Monthly number of entries into MMT before, during and after the closure of the Letten scene in February 1995, MMT retention rates, participants' socio-demographic and drug-related data.

FINDINGS: ARIMA modelling revealed 68 (95% CI = 31-105; p < 0.001) additional MMT admissions due to the dispersion of the open drug scene without a decrease in MMT retention rates. Socio-demographic and drug-related characteristics of patients entering MMT in the month of the closure did not significantly differ from other admissions.

CONCLUSIONS: Law enforcement strategies to eliminate open drug scenes may increase the demand for MMT. Sufficient treatment facilities for opioid dependence should be provided when law enforcement activities against open drug scenes are planned.