Determination of methylphenidate in Calliphorid larvae by liquid-liquid extraction and liquid chromatography mass spectrometry - Forensic entomotoxicology using an in vivo rat brain model

The aim of this study was to examine the potential forensic utilisation of blowfly larvae (Diptera: Calliphoridae) as an alternative toxicological specimen for the detection of the psychotropic model drug methylphenidate (MPH). MPH was extracted from biological matrices (rat brain, serum and Calliphorid larvae) by liquid-liquid extraction with recovery of >80%, and quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The LC-MS/MS assay was validated for entomotoxicological use and initially applied to male Sprague-Dawley rats (n = 6) that were dosed with MPH (20 mg/kg) ante-mortem. MPH could be detected in Calliphorid larvae (n = 15) reared on the rat brains at 3.2 ± 1.6 ng/g. Secondly, MPH-spiked porcine brain tissue (450 mg/kg) was used to investigate drug concentration in larvae over a period of 72 h. After larvae had feed for 60 h, MPH was detected at 19.8 ± 1.4 μg/g in the feeding larvae and at 3.5 ± 0.1 μg/g in the MPH-spiked porcine brain tissue. It could be advantageous to use Calliphorid larvae as an alternative toxicological specimen to detect alkaline labile drugs, such as MPH.