Determination of cannabinoids in plasma

Abstract

The use of cannabis in the medical industry is increasing. Tetrahydrocannabinol (THC)’s psychoactive properties and Cannabidiol (CBD)’s analgesic, neuroprotective, anticonvulsant, anti-inflammatory and anti-emetic properties contribute to the different conditions for which medical cannabis can be used. The aim of this study was to develop and validate a quick and efficient method to quantify THC in plasma, using High Performance Liquid Chromatography (HPLC), coupled with Ultraviolet (UV) detection. An analytical method to determine the concentration of THC in plasma was developed, and analytical parameters including stationary phase, mobile phase, detector, sample preparation technique, and biological matrix were identified. Analysis took place at the Pharmaceutical Synthesis and Technology Laboratory, at the University of Malta. The method was validated for accuracy, intra-day and inter-day precision, linearity, selectivity and stability, in compliance with the International Council of Harmonisation (ICH) guidelines. The method developed used protein precipitation in a 1:1.5 plasma to acetonitrile ratio, followed by vortex mixing and centrifugation as the sample preparation technique. Samples were then analysed using an Agilent 1260 Infinity II series chromatographic system, equipped with an ACE 5 C18 column as the stationary phase, and water (+0.1% acetic acid) and acetonitrile (+0.1% acetic acid), as the mobile phases, in a 30:70 ratio, using isocratic conditions. THC had a retention time of 16 minutes. The method was selective and specific, as confirmed by the chromatograms of the blank plasma sample. The method was found to be linear between 0.25 and 8μg/ml THC (R2=0.9945). The method can be applied to determine concentration of THC in plasma of patients taking medicinal cannabis. Determination of cannabinoids in biological fluids of patients can help provide more pharmacokinetic information leading to better dosing of cannabinoids and increased patient safety.