Frequent Injection Drug Use May Increase Risk

The number of different viral species in frequent injection drug users (IDUs) may be more than 60 percent higher than in non-users. Researchers found a direct correlation between how frequently an IDU injects drugs and the number of different varieties of HIV that exist within that drug user. The study, which appeared in the October 1999 issue of The Journal of Infectious Diseases, found that frequent injection drug use may provide a more fertile environment for the emergence of resistance to antiretroviral therapy, the drug treatment used to slow or suppress the progression of the HIV virus.

Richard B. Markham, MD, associate professor, Molecular Microbiology and Immunology, Johns Hopkins School of Public Health, said, "When there are a myriad of genetic mutations of the HIV virus inside the host, there is always the possibility that one of those mutations will cause resistance to drug therapy. It is a numbers game. Any activity that causes additional genetic mutations will increase the chances for appearance of those mutations that enable the virus to resist antiretroviral therapy."

Previous studies, performed before the availability of highly active antiretroviral therapy, have shown the course of HIV infection to be similar between IDUs and non-users, indicating that host factors controlling HIV infection were essentially equivalent between the two groups. However, the current study raises concerns that, when the host environment is changed by the addition of antiretroviral therapy, frequent drug users may be at a disadvantage. This study demonstrates the importance of reducing injection drug use in individuals being treated with antiretroviral agents. Treated individuals who continue to inject frequently should be monitored closely for the emergence of drug resistance.

This study was funded by a grant from the National Institutes of Health.