Cow Coke

Nearly a third of all cocaine seized in the United States is laced with a dangerous veterinary medicine - a livestock deworming drug that might enhance cocaine's effects but has been blamed in at least three deaths and scores of serious illnesses.

The medication called levamisole has killed at least three people in the United States and Canada and sickened more than 100. It can be used in humans to treat colorectal cancer, but it severely weakens the body's immune system, leaving patients vulnerable to fatal infections.

Scientific studies suggest levamisole might give cocaine a more intense high, possibly by increasing levels of dopamine, the brain's "feel-good" neurotransmitters.

Drug Enforcement Administration documents reviewed by the Associated Press indicate that 30 percent of all U.S. cocaine seizures are tainted with the drug. And health officials told the AP that most physicians know virtually nothing about its risks.

Authorities believe cocaine-makers are adding the levamisole in Colombia, before the cocaine is smuggled into the United States and Canada to be sold as white powder or crack.

Economic pressures may play a role. Decreased supply in the United States has raised cocaine prices and lowered street-level purity. Cocaine traffickers may believe levamisole adds an extra boost to an otherwise weakened product.