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MIAMI BEACH -- People who use cocaine contaminated with the veterinary drug levamisole may experience more than just dermatological effects, including end-organ damage and stroke, researchers reported here.

In a single-center review of cases, most patients who'd taken the adulterated drug not only had darkened skin lesions caused by blocked blood flow, but also had some form of end-organ damage, including blood in the urine and elevated liver enzymes, reported Lindsay Wilson, MD, of the University of Utah in Salt Lake City, during a poster session at the American Academy of Dermatology meeting.

Some patients also had a stroke within a few weeks of their initial diagnosis, and one had deep vein thrombosis (DVT) within a few days, Wilson reported.

"I think it's important to remember that there are a lot of people who use cocaine, levamisole is out there, and the consequences are more than just a purpura that you can see," she said.

Levamisole is an immunomodulator that was once prescribed for conditions such as rheumatoid arthritis and inflammatory bowel disease. But the FDA pulled it from the market in 2000 due to side effects such as the dark skin lesions of retiform purpura as well as agranulocytosis.

The drug is still widely available, however, because it's used in veterinary medicine to kill parasitic worms.

The U.S. Drug Enforcement Agency first detected it in seized cocaine in 2005, and currently estimates it to be found in about 80% of the overall cocaine supply.

Researchers suspect it's a favored adulterant because it can increase dopaminergic responses to cocaine and is also metabolized into an amphetamine-like byproduct, boosting the drug's effects. Also, it blends well and is stable in the crack formulation of the drug, Wilson said.

Plus, it passes drug dealers' purity testing with bleach, looking pure even when it is not. The incentive to dilute the drug has been strong in South American countries which have easy access to levamisole in their agrarian economies, she added.

Given that the prevalence of cocaine use is estimated to be 2.6% in the U.S., the effects of levamisole-contaminated cocaine could be widespread, Wilson said.

She reviewed seven of the eight cases of levamisole purpura that presented at her institution between 2007 and 2010. The majority of the patients were women with a mean age of 51.

All patients had "quite impressive retiform purpura with inflammatory borders," with the distinguishing feature of purpura on the ears, a common side effect reported when the drug was on the market.

Only one patient was tested for levamisole and the other cases were assumed to be due to the immunomodulator because "every other cause of retiform purpura was eliminated," Wilson said, adding that the drug is difficult to detect because its half-life is 5.5 hours and few labs offer a specific test for it.

The general pathology is a mix of small vessel vasculopathy with a secondary vasculitis and patients generally had fever, arthralgia, and anemia, she reported.

Patients had a muddled inflammatory profile, with a mix of ANCA positivity as well as inconsistent findings in terms of antiphospholipid antibodies, protein C/S, and homocysteine. "So when you can't put the clinical picture together, if they use cocaine, think of levamisole," she said.

Most patients did, however, have some form of end-organ damage: most commonly vasculitis with gross hematuria and elevated liver enzymes that decreased when the retiform purpura went away.

Also, two of the patients had strokes within 3 weeks of their diagnosis of levamisole purpura, and one had DVT a few days after the diagnosis.

"This is a strongly thrombotic episode that can have severe consequences for patients," Wilson said, adding that aspirin or warfarin (Coumadin) may help with the "thrombotic storm" but needs to be carefully balanced against the risk of hemorrhage typical of retiform purpura.

Wilson concluded that the nearly 8 million people in the U.S. who use cocaine are at risk of these complications and clinicians are likely to see these kinds of cases so should be aware of the more problematic complications.

Jeffrey Miller, MD, of Penn State University in Hershey, Pa., who moderated the session at which the findings were presented, agreed that in addition to the common retiform purpura seen with levamisole-contaminated cocaine, there are also "systemic complications that can be life-threatening."

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