In addition to triggering life-threatening cardiovascular episodes, cocaine can be deadly in another way. According to a report published today in the Annals of Internal Medicine, the drug may also lethally impair the body's ability to cool itself when exposed to elevated temperatures. When used in sweaty settings such as crowded nightclubs and all-night raves, even tiny amounts of the illicit drug seem to disturb three of the body's temperature-lowering mechanisms. According to lead author Craig G. Crandall of the University of Texas Southwestern, "Individuals abusing cocaine, especially in hot temperatures, wont perceive that they are hot and are, therefore, less likely to drink water or to find cooler conditions."

Scientists have known for some time that cocaine can raise body temperatures to fatal levels. Researchers formerly thought, however, that only increased heat production--through agitation and elevated muscular activity--caused this dangerous escalation. Now Crandall and his colleagues have discovered that along with causing the body to generate more heat, cocaine also prevents it from cooling off when exposed to overly high temperatures. The team tested seven healthy volunteers who had not previously tried cocaine. The subjects received small doses of the drug on inside of their noses and ingested thermometers to measure their internal body temperatures. The researchers then elevated the volunteers' body temperatures using suits stitched with hollow hot-water-filled tubes and measured their internal responses. As the cocaine further increased the subjects' body temperatures, it also rendered them less conscious of overheating. What is more, the drug decreased sweating and prevented blood vessels on the skin from dilating and allowing heat to be released. It seems that as cocaine users are exposed to higher and higher temperatures, they become less able to cool themselves off.

Approximately 25 million Americans have tried cocaine. Fatal overheating can occur just as easily in recreational users as in longtime addicts, and, judging from the new findings, the risk may be heightened for experimental revelers partying at a sweltering late-night bash. The underlying mechanism of this effect is not entirely understood. But because the thresholds for the activation of sweating and blood vessel dilation, as well as for perceiving heat stress, are mediated through the central nervous system, the authors say that "this is the most concrete evidence that cocaine acts centrally to alter thermoregulatory responses." Crandall adds, "Identifying the molecular mechanisms of cocaine-induced hyperthermia [overheating] could lead to the identification of new drug targets that may reduce cocaine-related deaths."