The cocaine cutting agent levamisole is frequently detected in cocaine users.

Cocaine use in Australia is increasing, with approximately 2.5% of the surveyed population having used cocaine. In the USA, levamisole, a widely used anti-helminthic veterinary drug has been increasingly detected as a cutting agent in cocaine seizures. Levamisole is known to cause agranulocytosis in humans. We ascertained the prevalence of levamisole-adulterated cocaine, detectable in the urine from patients that had undergone a pathology request for a urine drug screen. We assayed routinely requested urines that were positive for cocaine on immunoassay with liquid chromatography high resolution quadrupole time of flight mass spectrometry (LC-QToF). We investigated available urine samples from a period of 2 years that had a positive result for cocaine. In addition, we examined samples that were below the cut-off for cocaine on immunoassay. Specimens were analysed for the presence of levamisole and other 'unknown' drugs. In the period under investigation the laboratory examined 3665 urine samples for cocaine: 1.4% (n = 51) of the samples were positive for cocaine by immunoassay and half of these (n = 26, 51%) were further examined by LC-QToF. In addition, we examined 10 samples that were negative by immunoassay (as defined by AS/NZS 4308:2008). Levamisole was detected in the urine of cocaine users in approximately 75% of cases. Other illicit drugs were also frequently found in this cohort. The most common illicit drugs detected were methamphetamine, ecstasy and cannabis. Australian cocaine is widely adulterated with levamisole. Cocaine users are at risk of levamisole related health problems in addition to the problems related to cocaine.