Prevalence of levamisole and aminorex in patients tested positive for cocaine in a French University Hospital.

Context: The prevalence of levamisole in urine samples of subjects positive for cocaine in the US was estimated at 78% (95%confidence interval or CI: 73%-83%). However, levamisole was not quantified, and at the time of this report, aminorex was not known to be a possible metabolite of levamisole in human. Moreover no data are available in Europe.
Objective: The aim of this study was to determine the prevalence and concentration of levamisole and aminorex in positive cocaine urine toxicology tests, and in serum samples of cocaine-positive subjects driving under the influence of drugs or forensic autopsies.
Materials and Methods: Consecutive urine toxicology samples tested positive for cocaine by immunoassay (EMIT, Siemens) from April to May 2014 at the toxicology laboratory of a French University Hospital, and blood samples of cocaine-positive subjects driving under the influence of drugs or forensic autopsies from April to December 2014 were analyzed by liquid chromatography-tandem mass spectrometry or LC-MS/MS (3200 QTrap, AB Sciex) to detect and quantify the presence of levamisole and aminorex.
Results: Forty-two urine samples tested positive for cocaine in 39 patients (79.5% males) with a median age of 43 [range: 20-51] years. Toxicological analyses were mainly required by addictions care centers (n = 17; 40%) in the context of the routine management of addict patients. Cocaine concentrations were above the limit of quantification for 33 patients, with a median value of 228 [0-645,000] ng/ml. Levamisole was detected in 32 urine samples (76%) (median concentration: 1,430 ng/ml, range: 30-258,000). Aminorex was never detected. During the study period, levamisole was detected in 87.5% of cocaine-positive blood samples of the subjects driving under the influence of drugs or forensic autopsies.
Discussion: In this prospective study, the prevalence of levamisole in cocaine-positive samples was 76%. Over this period, although clinical complications related to cocaine use were reported (agitation, road accident, and cardiac arrest), no complication specifically related to levamisole or aminorex was reported.
Conclusion: Our results show a high prevalence of levamisole in samples of subjects positive for cocaine, close to the prevalence found in the US. This high prevalence raises issues with respect to well-identified health risks associated with regular consumption of levamisole.