Manufacturers of the illegal street drug cocaine commonly cheapen or adulterate their products with other substances in order to save money and make their drug supplies go farther. Since roughly 2003, one of the substances most frequently added to cocaine has been levamisole, a medication banned from human use in the United States. Cocaine users exposed to levamisole can develop a condition called agranulocytosis, which occurs when the body stops producing sufficient amounts of vital white blood cells called granulocytes. Without a proper amount of granulocytes in their bodies, cocaine users have significantly increased risks for a variety of dangerous and potentially deadly infections. Levamisole Basics Levamisole was originally developed in the 1960s and subsequently used in humans for purposes such as treating parasitic worm infections, accelerating the effects of certain chemotherapy regimens, and regulating immune system activity. However, in 2000, the US Food and Drug Administration banned human use of the drug because of its ability to wreak havoc on the production of white blood cells. The drug remains on the market as a veterinary product. As noted previously, levamisole began to show up in cocaine batches in the US in the early 2000s. The US Drug Enforcement Agency estimates that roughly 70 to 80 percent of all of the cocaine available in America contains levamisole. According to a study review published in 2012 in the journal Clinical Toxicology, the medication has several different brain effects that likely support or boost the brain effects of cocaine. Agranulocytosis Basics The human body produces its white blood cells and other blood components in bone marrow, a specialized tissue found in the core of long bones in the skeleton. Granulocytes are a diverse group of white blood cells that contain tiny particles, called granules, in their interiors. Specific types of these cells include neutrophils, eosinophils and basophils; all three of these cell types play an essential role in the body\u2019s immune response to viruses, bacteria, fungi, and other types of foreign invaders in the bloodstream. As noted previously, in agranulocytosis, the bone marrow stops making adequate amounts of granulocytes. In most cases, people with the disorder stop producing sufficient numbers of neutrophils; for this reason, some health care professionals imprecisely refer to agranulocytosis as neutropenia. However, the condition can also result from an inadequate supply of eosinophils (also known as eosinopenia) or, in relatively rare circumstances, from an inadequate supply of basophils (also known as basopenia). Strictly speaking, true agranulocytosis involves a much more severe loss of white blood cells than occurs in people with neutropenia, eosinopenia, or basopenia. Apart from levamisole, medications capable of producing agranulocytosis include penicillin and several other antibiotics, naproxen and several other nonsteroidal anti-inflammatory drugs (NSAIDs), clozapine, and certain other antipsychotic drugs, and a variety of anticonvulsant or antiepileptic drugs. Additional potential causes of the disorder include toxin exposure, leukemia, a vitamin B12 deficiency, a vitamin B9 deficiency, chemotherapy, spleen enlargement, and conditions called aplastic anemia and myelodysplastic syndrome. Because of the immune system suppression associated with agranulocytosis, people with the disorder have seriously increased risks for a range of dangerous infections, including pneumonia, a blood-borne bacterial infection called septicemia, and the human immunodeficiency virus (HIV). Without proper treatment to correct their white blood cell deficiencies, affected individuals can easily die from the effects of an agranulocytosis-related infection. Considerations in Cocaine Users Levamisole adulteration is almost certainly the underlying cause of otherwise unexplained agranulocytosis in many people who use cocaine, according to a study published in 2010 in the American Journal of Clinical Pathology. In many instances, doctors successfully treat cocaine-related agranulocytosis in their patients without realizing the role of drug use in the disorder\u2019s origin; roughly 27 percent of these patients develop agranulocytosis again, apparently as the consequence of re-exposure to levamisole-adulterated cocaine, the authors of the review in Clinical Toxicology report. No one knows for sure how many cocaine users develop agranulocytosis or dangerous infections related to the presence of the disorder. In addition to its ability to trigger agranulocytosis, levamisole can cause a flesh-rotting syndrome when used as a dewormer in livestock populations. According to a study published in 2011 in the Journal of the American Academy of Dermatology, the medication may also be the underlying source of a similar flesh-eating condition found in limited numbers of cocaine users. Apparently, affected individuals have an unusual level of susceptibility to levamisole\u2019s flesh-damaging effects.