Agranulocytosis After Consumption of Cocaine Adulterated With LevamisoleFREE

Background: Levamisole is a veterinary antihelminthic previously used as an immunomodulator in rheumatoid arthritis and as adjuvant therapy in the treatment of colorectal cancer. It is no longer available in North America for human use but is available in the United States and South America for veterinary administration.

Since 2004, pharmaceutical agents have been found in cocaine supplies in North America and Europe (1). Levamisole contaminated 30% of cocaine seized by the U.S. Drug Enforcement Agency from July to September 2008 (U.S. Department of Justice, Drug Enforcement Administration. Cocaine Signature Program Report. January–October 2008. Internal document.) and 11% of cocaine samples tested in Alberta, Canada, from April to December 2008 (Office of Research and Surveillance, Health Canada. Personal communication.). Levamisole causes reversible agranulocytosis in up to 20% of cases (2), but the clinical effects of cocaine adulterated with levamisole have not been described.

Objective: To describe 5 patients with severe agranulocytosis after exposure to cocaine and levamisole.

Case Report: Between July and November 2008, 5 patients with a history of cocaine use were hospitalized for agranulocytosis, fever, and a variety of infectious complications in northern Alberta, Canada (Table). Two patients had iron deficiency anemia, and 1 had chronic stable hepatitis C. Patients had no history of medication use or nutritional deficiencies, malignant conditions, or rheumatologic disorders that can cause agranulocytosis. Serum vitamin B₁₂ and erythrocyte folate levels were normal. Imaging of the chest, abdomen, and pelvis with radiography and ultrasonography or computed tomography did not show any malignant conditions. Bone marrow examination in 2 patients showed reduced granulocytic proliferation and maturation (Figure) consistent with past reports of agranulocytosis from levamisole (3).

Urine toxicology testing using gas chromatography/mass spectrometry (GC/MS) detected cocaine or its metabolites and levamisole. The presence of the drugs was verified by injecting urine extracts into the GC/MS and then comparing readings with those from pure standards according to 2 parameters: drug fragmentation pattern (total ion mass spectra) and time for the drug to pass through the system (retention time). Because lupus anticoagulant has been associated with levamisole use (4), we tested for it and detected it in all 5 patients with confirmed levamisole exposure.

All patients fully recovered with use of filgrastim, intravenous antibiotics, and close monitoring. One patient presented with another episode of fevers and agranulocytosis 3 months later, when cocaine and levamisole were again found on urine testing. We treated 6 additional patients with a history of cocaine use who were hospitalized for agranulocytosis and fever. We suspected levamisole-adulterated cocaine as a cause but could not confirm the presence of the drug by using toxicology testing in these patients.

Discussion: It is unknown why pharmaceutically active agents are added to the cocaine supply; it is possible that cocaine producers or suppliers think that the agents enhance the drug's effects or attenuate its side effects. Cocaine achieves its psychoactive effects by increasing dopamine concentrations in the euphoric centers of the brain, and animal studies have found that levamisole also increases dopamine levels in these regions (5). We speculate that levamisole may potentiate the euphoric effects of cocaine by further increasing brain dopamine levels.

We did not test cocaine samples in the patients' possession for levamisole, so we cannot directly attribute the agranulocytosis to levamisole or prove that the cocaine was adulterated with levamisole. To directly connect levamisole to agranulocytosis, we would have to examine its effects on in vitro stem cell growth (by granulocyte-macrophage colony-forming unit clonogenic assay) (6).

Other nonprescribed medications consumed and not detected on toxicology testing, or other adulterants, might also explain the agranulocytosis. Nevertheless, we advise clinicians to consider the possibility of cocaine use and, specifically, the use of levamisole-adulterated cocaine, in patients with otherwise unexplained fever and agranulocytosis. Prompt urine toxicology testing is essential because levamisole has a short-elimination half-life of 5.6 hours (7) and little of the parent drug (2% to 5%) is detected in urine (8). In addition, cocaine metabolites are detected up to 3.4 days on average after last use (9). Because levamisole is not detected by routine immunoassay toxicology screening tests, other techniques, such as GC/MS, are required.

Conclusion: Cocaine adulterated with levamisole may be a cause of febrile agranulocytosis in cocaine users. Clinicians should consider the possibility of exposure to levamisole-adulterated cocaine in patients with otherwise unexplained fever and agranulocytosis.

Nancy Y. Zhu, MD

Donald F. LeGatt, PhD

A. Robert Turner, MD

University of Alberta

Edmonton, Alberta T6G 2B7, Canada