Methamphetamine (METH) use and HIV infection frequently co-exist, perhaps because METH use is associated with high-risk behaviors. The current study evaluated potential interactions between METH use and HIV infection among current METH users, abstinent former users, and subjects with no history of METH use. The researchers measured viral load in cerebrospinal fluid as well as blood plasma to address the possibility that the effects of METH use on viral load are amplified in the central nervous system. The investigators grouped subjects according to current HAART use and analyzed their self-reported adherence to assess the potential effect of METH use on HAART efficacy.

Participants were 230 volunteers enrolled in various longitudinal studies at the HIV Neurobehavioral Center, University of California-San Diego between 1996 and 2002. The researchers classified subjects into three groups: METH+Tox-, 66 subjects who had previous METH dependence but had been free of METH dependence for at least 30 days at the time of evaluation, and who had negative urine toxicology results for METH; METH-Tox-, 76 study participants who were never METH dependent and who had negative urine toxicology results at the time of evaluation; and Tox+, active METH users with positive urine toxicology results at the time of evaluation.

"Tox+ subjects' plasma virus loads were significantly higher than Meth+Tox- and METH-Tox- subjects'; cerebrospinal fluid virus loads showed a similar but nonsignificant trend," the authors found. "Stratification by use of highly active antiretroviral therapy (HAART) revealed that virus loads were higher only in those Tox+ subjects who reported receiving HAART. In contrast, abstinent former METH abusers (METH+Tox-) receiving HAART effectively suppressed viral replication," the researchers wrote.

"Despite concerns that the complexities of HAART therapy make it impractical for persons with a history of drug abuse, our findings demonstrate that former METH users who maintain abstinence can effectively suppress HIV replication with potent ART. These data suggest that providers involved in the clinical care of HIV-infected persons who are METH users will need to make efforts to get their patients into substance abuse treatment programs to assist them in achieving stable abstinence. Once abstinence is achieved, the responses to ART by former METH-dependent persons are similar to those of non-substance abusing control subjects," the researchers concluded.

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