Cessation of injection drug use and change in injection frequency: the Chicago Needle Exchange Evaluation Study.

AIMS To examine the effect of a needle exchange program (NEP) on incidence of injection cessation and change in injection frequency; to explore predictors for injection cessation and change in injection frequency; and to assess whether injection quitters transitioned to non-injected drug use. DESIGN AND SETTING Between 1997 and 2002, 901 injection drug users (IDUs) were recruited from an NEP program or an area with no NEP in Chicago, Illinois, interviewed for drug use behaviors, tested for HIV and followed for three annual visits. All participants were exposed to prevention services targeting HIV and drug abuse. MEASUREMENTS Injection cessation was defined as no injection drug use since the last interview, and changes in the number of injections in a typical month were examined. FINDINGS Sixteen per cent of study participants reported stopping injection for a median duration of 16 months, and most of them also ceased rather than initiated the use of non-injected drugs. Those who continued injecting reduced their injection frequency by 12% per year, on average. Independent predictors of injection cessation were infrequent injection at baseline, younger age and injecting with others. NEP use was not associated with injection cessation and change in injection frequency. CONCLUSION These results did not support the hypothesis that NEP use influences the frequency of injection over time. One-sixth of IDUs stopped injection for more than 1 year, providing a substantial window for relapse prevention interventions.