Needle sharing and participation in the Amsterdam Syringe Exchange program among HIV-seronegative injecting drug users.

To enhance the prevention of human immunodeficiency virus infection, factors related to regular participation in the Amsterdam Syringe Exchange and the borrowing of syringes were studied in 131 HIV-seronegative injecting drug users in a 1989-90 survey. A total of 29 percent of the users reported borrowing syringes, that is injecting drugs at least once in the past 4-6 months with a needle or syringe previously used by someone else. Users at increased risk of borrowing are previous borrowers, long term moderate-to-heavy alcohol users, current cocaine injectors, and drug users without permanent housing. Regular clients of the syringe exchange, when compared with other injecting drug users, were found more often to be frequent, long term injectors. They borrowed slightly less often than other users, but this was not statistically significant, even after controlling for frequency of injecting or other potential confounders. The results suggest that, 5 years after the start of the Amsterdam Syringe Exchange, drug use characteristics govern an individual injecting drug user's choice of exchanging or not exchanging syringes. The conclusion is that it seems more important to direct additional preventive measures at injecting drug users with an increased risk of borrowing rather than at users who do not participate in the syringe exchange or who do so irregularly.