Cocaine May Blunt Immune Resistance to Infection
By Karla Gale
Intravenous cocaine appears to blunt the interleukin-6 (IL-6) response to
pro-inflammatory challenge, investigators at Harvard Medical School report,
which helps explain why cocaine users are more susceptible to infection.
Cocaine abuse is associated with increased susceptibility to infection and
enhanced progression of HIV disease (see Reuters Health reports, February 14 and
May 22, 2002). To investigate why, Dr. John Halpern and colleagues evaluated the
effects of cocaine on hormone and cytokine responses.
Their placebo-controlled trial involved placement of an indwelling venous
catheter, which leads to inflammation of the surrounding tissue and release of
IL-6. "Thus, catheter placement provides a model for examination of cocaine's
immunological effects," Dr. Halpern's group explains in the March issue of the
Journal of Clinical Endocrinology and Metabolism.
"The model we used is very novel, and involves a way of perturbing the immune
system safely, and seeing how the body reacts," Dr. Halpern told Reuters Health.
The trial included 30 known cocaine users who had used the drug within the
previous month. The subjects would be defined as "occasional users," Dr. Halpern
noted. "Subjects were excluded if they had ever met any of the criteria for
cocaine dependence."
The researchers placed an indwelling catheter into the antecubital vein of the
subjects' nondominant arm 30 minutes prior to i.v. injection of cocaine 0.4
mg/kg or saline into the contralateral arm.
After placebo injection, plasma levels of ACTH, cortisol and DHEA remained
unchanged, but they increased significantly after administration of cocaine (p <
0.002 for each). Hormone levels peaked within 40 minutes, all returning to
baseline levels by 180 minutes after cocaine infusion.
IL-6 levels rose sharply between 150 and 210 minutes after catheter placement,
but serum concentrations were significantly lower at 240 minutes after
administration of cocaine than after placebo (3.85 pg/mL versus 11.64 pg/mL; p =
0.0019). Findings were similar for the 16 female subjects and the 14 male
subjects.
The increased risk of infection among those who abuse drugs is assumed to be
correlated with lifestyle, high-risk behaviors, poor nutrition, and dirty
needles, Dr. Halpern said. "But here's a drug that makes you feel confident to
begin with. People may think, 'I don't engage in those high risk behaviors, so I
say I can handle it.'"
"Meanwhile, this drug is silently altering how the immune system responds to a
triggering event," the researcher added. "So you may end up engaging in
high-risk sexual behavior because you're under the influence of the drug. The
drug is priming tissue to not fight off infection right at the point when the
individual is most in need of a strong immune response."
"If cocaine knocks down immune system by only 5%, but you add to that poor
nutrition and high risk behaviors, that 5% could put you over the top--and you
get HIV."
03/19/03
J Clin Endocrinol Metab 2003;88:00-00.
http://www.hivandhepatitis.com/recent/misc/031903s.html
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