In September I noted government warnings about cocaine cut with levamisole hydrochloride, a veterinary drug that can impair people's immune systems, leaving them vulnerable to disfiguring, disabling, and potentially deadly diseases. As of July, according to the Drug Enforcement Administration, about 70 percent of the cocaine entering the country was tainted by levamisole, which may be favored as a cutting agent because it boosts the stimulant's perceived effect. The San Francisco Chronicle reports that levamisole-related medical problems are starting to turn up in that city:

So far, eight cases of illness caused by the drug levamisole have been identified in San Francisco, one of a handful of cities in the country where pockets of sickness caused by the drug have been found....

Levamisole can significantly reduce the number of white blood cells in the body, a condition called agranulocytosis. Symptoms include fever, swollen glands, painful sores in the mouth and anus, and an infection that won't go away. In San Francisco, patients with levamisole poisoning also are getting serious skin conditions that make their skin look black.

In a group of 200 patients at San Francisco General Hospital who tested positive for cocaine, 90 percent also tested positive for levamisole. That figure may exaggerate the prevalence of levamisole in cocaine, since patients who test positive for cocaine are not necessarily representative of cocaine users in general. In any case, most of the patients who had been exposed to levamisole did not get sick as a result. "The big question we have right now," the associate chief of the hospital's toxicology lab tells the Chronicle,"is, if 90 percent of cocaine users in San Francisco are positive for levamisole and are being exposed to this compound, then why aren't 90 percent of them in the emergency room with these side effects?" It may be that the drug has a dramatic effect only on people who are predisposed to immune system problems. It is also possible that milder reactions are being misidentified as flu, or that repeated exposure is necessary, in which case a larger percentage of cocaine users can be expected to get sick over time.

As I emphasized in September, whatever the magnitude of the levamisole hazard, we have prohibition to thank for it:

You won't find levamisole in legal, pharmaceutical cocaine, just as you won't find methanol in the whiskey you get at your local liquor store. The main reason for that is not government regulation (although there's none of that in a black market) but the need to compete for customers in a legal, open market where fraud and negligence are punished not only by law but by the loss of business. By making such competition impossible, prohibition creates uncertainty about the quality and purity of drugs, and more aggressive enforcement only makes the problem worse. To the extent that the government succeeds at its avowed goal of reducing cocaine purity, for example, it encourages more use of levamisole, resulting in more disease and death. Anyone who supports this policy has to accept the resulting casualties as a necessary cost of deterrence.

[Thanks to Paul Rako for the tip.]