Development and method validation of a sampling technique for a reproducible detection of synthetic cannabinoids in exhaled breath using an in vitro pig lung model

Abstract

Alternative matrices, especially exhaled breath (EB), have gained increasing attention for a few years. To interpret toxicological findings, knowledge on the toxicokinetic (TK) properties of a substance in EB is indispensable. Whilst such data are already accessible for various drugs (e.g. Δ9-tetrahydrocannabinol), they are still not available for new psychoactive substances, particularly synthetic cannabinoids (SCs). As SCs raise a high public health concern, the aim of this study was to assess these data in future TK studies in pigs. For this purpose, an in vitro sampling technique of EB was initially developed, being prospectively applied to anesthetized and ventilated pigs for the detection of SCs in a controlled and reproducible manner as exemplified by cumyl-5F-P7AICA. Furthermore, a method for the qualitative and quantitative detection of cumyl-5F-P7AICA in EB using glass fiber filters (GFF) was established und fully validated. Therefore, cumyl-5F-P7AICA (0.5 mg/mL in ethanol abs.) was initially nebulized using a ventilation machine and a breathing tube, as they are also used in surgeries. The aerosol was delivered into a simulated pig lung. To collect EB, a pump was connected to that part of the breathing tube, that contains EB (expiratory limb), and sampling was performed repeatedly (n=6) for 15 min (2 L EB/min) each using GFF. For extraction of the substance, the GFF were macerated with acetone and the remaining experimental components were rinsed with ethanol. After sample preparation, the extracts were analyzed by LC-MS/MS. In the complete experimental setup, about 40% of the initially nebulized cumyl-5F-P7AICA dose was found with 3.6 ± 1.3% being detected in the GFF. Regarding the comparably high loss of substance, the open ventilation system and a conceivable adsorption of the SC in the ventilator have to be considered. However, the herein introduced approach is promising to determine the TK properties of cumyl-5F-P7AICA in EB.