"Poppers," some other drugs, may increase HIV infection risk.

Users of amphetamines ("crystal"), hallucinogens, or inhaled nitrites ("poppers") had higher rates of HIV infection than non-users, (1) in an analysis of the Vaxgen trial data presented at the 11th Conference on Retroviruses and Opportunistic Infections, February 8-11, 2004.

This information was collected from 4,697 high-risk HIV-negative men who have sex with men, who were enrolled at 56 clinical-trial sites in the U.S. for the 36-month trial. Overall, there were 2.8 HIV infections per 100 person-years--already considered a high number. But amphetamine users had 4.5 infections per 100 person-years, hallucinogen users had 4.0, and poppers users had 3.6. In this high-risk cohort there were many more users of poppers than of the other two put together--2176 reported poppers use, vs. 901 amphetamines and 603 hallucinogens--suggesting a potentially large impact on the spread of HIV.

The drugs may be having this effect by making people more likely to take risks they would otherwise have avoided. Some drugs might also affect the immune system directly. In August 1999 AIDS Treatment News noted animal studies showing that exposure to "poppers" increased cancer growth (2) and bacterial growth (3), probably by suppressing the animals' natural immunity.

Comment

The higher rates of HIV infection found could also be due to selection bias--if, for example, those who accept the risks of using illegal drugs also tend to take more risks in other areas, such as unprotected sex. The difference in this case is that the drugs would not be contributing to increased infection, but only identifying those already at higher risk. Both mechanisms could be involved, with drug both contributing to infection and also indicating who was already more likely to be infected.

References

(1) M Ackers, A Greenberg, C Lin and others. High HIV incidence among men who have sex with men participating in an HIV vaccine efficacy trials, United States, 1998-2002. 11th Conference on Retroviruses and Opportunistic Infections, San Francisco, February 8-11, 2004. [abstract 857]

(2) Soderberg LSF. Increased tumor growth in mice exposed to inhaled isobutyl nitrite. Toxicology Letters, 1999; volume 104, pages 35-41.

(3) Schafer R, Barnett J, Soderberg L, and Damiani C. Pulmonary exposure to isobutyl nitrite reduces resistance to a respiratory infection. 10th International Congress of Mucosal Immunology, Amsterdam, June 27 to July 1, 1999.