Résumé
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.