Hostile effects of levamisole

One of the more serious side effects of levamisole is agranulocytosis, which is a decrease in white blood cells.In particular, neutrophils appear to be most affected.This occurs in 0.08–5% of the study population.It has been used as an adulterant of cocaine, resulting in serious side effects manifested by levamisole-induced necrotic syndrome in which erythematous painful papules can appear on almost any part of the skin.

Metabolism 

Levamisole is readily absorbed from the gastrointestinal tract and metabolized in the liver.The time to peak plasma concentration is 1.5-2 hours.The plasma elimination half-life is fairly rapid, 3-4 hours, which may result in undetectable levamisole toxicity.The metabolite half-life is 16 hours.Levamisole is primarily excreted by the kidneys, with about 70% excreted within 3 days. Only about 5% is excreted as unchanged levamisole.Drug testing of racehorse urine revealed that equine metabolites of levamisole include pemoline and aminorex, which are stimulants banned by racing authorities.Further testing confirmed aminorex in human and canine urine, implying that humans and dogs also metabolize levamisole to aminorex,although it is unclear whether plasma aminorex is present at any appreciable level. Blood samples taken after oral administration of levamisole up to 172 hours post-dose did not show any plasma aminorex levels above the limit of quantification (LoQ).Furthermore, in cocaine-positive plasma samples, 42% of which contained levamisole, aminorex concentrations above the LoQ were never reported.

Body fluid testing

Levamisole can be quantified in blood, plasma or urine as a diagnostic tool in clinical intoxication situations or to assist in forensic investigations of suspicious deaths involving adulterated street drugs.Approximately 3% of an oral dose is eliminated unchanged in human 24-hour urine.Post-mortem blood levamisole concentration of 2.2 mg/L in a woman who died of a cocaine overdose.