According to a letter in the June 1 issue of the Annals of Internal Medicine, cocaine mixed with the veterinary anti-parasitic drug levamisole hydrochloride can cause "bilateral necrosis of earlobes and cheeks"—or, as the Yahoo! News headline puts it, "Contaminated Cocaine Can Cause Flesh to Rot." Doctors already have reported that levamisole in cocaine can cause agranulocytosis, a reduction in white blood cell production that leaves the body vulnerable to various infections. But this week's letter, which describes two cases, is the first report of skin lesions like these tied to consumption of levamisole-tainted cocaine. Both side effects have been seen in clinical studies of levamisole, which is used in humans to treat cancer and autoimmune disorders.
According to the U.S. Centers for Disease Control and Prevention, about 70 percent of cocaine seized at the border in 2009 contained levamisole, up from around 10 percent a few years before. The drug's popularity as a cutting agent may have increased because it enhances cocaine's perceived effects while reducing its cost. But even though most cocaine consumed in the U.S. (perhaps as much as 80 percent) now contains levamisole, and about 6 million Americans use cocaine every year, there have been few reports of serious side effects from the contaminant, which suggests that they do not occur very often. Presumably people whose immune systems are already weak are especially vulnerable. As I noted last September, when the federal government started warning the public about levamisole in cocaine, whatever hazard it represents is entirely attributable to prohibition, which makes drugs more dangerous by encouraging practices that would never survive in a legal, open, competitive market. Just as drinkers no longer need to worry about methanol in their liquor, medical users of legally produced cocaine need not worry about levamisole.