Cocaine, levamisole, and the white blood count
December 6, 2011, 12:11 am
Levamisole Exposure and Hematologic Indices in Cocaine users. Chai PR et al. Acad Emerg Med 2011 Nov;18:1141-1147.
As TPR has reported previously, the majority of cocaine samples seized at U.S. borders in recent years have been contaminated with levamisole, a veterinary anthihelminthic agent that is not approved for human use because of its association with cases of leukopenia and agranulocytosis. This idiosyncratic reaction has been described in cocaine users with proven or probable exposure to levamisole.
This paper, from the Alpert Medical School/Brown University of Providence, retrospectively reviewed charts of patients admitted to five hospitals in their system who screened positive for the cocaine metabolite benzoylecognine and had a complete blood count done at the time of drug testing. These patients were assigned to one of two groups based on the presence of absence of levamisole in the urine drug screen. (Remarkably, the authors’ hospital utilized a comprehensive drug screen that could test for more than 1000 drugs, including levamisole). Primary outcomes measures were total white blood count (WBC), absolute neutrophil count (ANC), and absolute lymphocyte count (ALC).
Ninety five eligible patients were identified. Of these, 47 were levamisole-positive, and 48 levamisole-negative. The authors found that there was no significant difference in WBC, ANC, or ALC between the two groups. Unfortunately, there is really nothing of clinical importance that we can make of this finding. Since onset of levamisole-associated neutropenia may occur as late as 3 weeks after exposure — much longer than the limit of detection for levamisole — it is certainly possible that the low WBC seen in levamisole-negative patients had in fact been caused by exposure to the drug.
in fairness, the authors make this point in their discussion of study limitations. They also make some important points in passing:
- Cases of levamisole-associated neutropenia or aganulocytosis often present with soft-tissue infections or oropharyngeal complaints.
- Vasculitis is another adverse effect from exposure to cocaine contaminated with levamisole, frequently with impressive necrotic purpuric lesions of the ears and cheeks.
- The reason so many cocaine samples are contaminated with levamisole is not really known.