Quantification of Furanylfentanyl and its Metabolites in Human and Rat Plasma Using LC-MS-MS.

ABSTRACT

Fentanyl analogs (novel and traditional) continue to impact the ever-growing opioid epidemic. Furanylfentanyl (FuF) is one analog equipotent to fentanyl that has documented involvement in thousands of intoxication and fatality cases around the world. Due to its prevalence, toxicologists need to improve detection and understanding of this analog. A method for the quantification of FuF and its metabolites (4-ANPP, furanyl norfentanyl (FuNorF)) in a small volume (100 µL) of human plasma by LC-MS-MS was developed and validated according to ANSI/ASB Standard. The method was cross validated in rat plasma for a future pharmacokinetic (PK)/pharmacodynamic (PD) study. In human plasma, calibration ranges were 0.025-25 ng/mL (FuF and 4-ANPP) and 0.5-25 ng/mL (FuNorF). Limits of detection were 0.0125 ng/mL (FuF and 4-ANPP) and 0.25 ng/mL (FuNorF). Lower limits of quantification coincided with lowest calibrator concentrations of 0.025 ng/mL (FuF and 4-ANPP) and 0.5 ng/mL (FuNorF). Precision and bias values were determined to be acceptable for all analytes. Matrix effects were acceptable for all analytes (-8.6-25.0%), except FuNorF with suppression >25%. Extraction recoveries ranged from 84.5 to 98.1%. No carryover or endogenous interferences were observed. Qualitative interferences with 4-ANPP were observed from some n-acyl substituted fentanyl analogs predicted to be low-concentration standard impurities. Analytes were stable under all conditions and dilution integrity was sustained. The method was successfully cross validated in rat plasma with acceptable bias (-7.4-8.4%), precision (within-run < 19%CV and between-run < 12.6%CV), matrix effects (-9.3-17.2%, except FuNorF with >25% suppression), recoveries (79.2-94.5%) and dilution integrity (1/2 and 1/10).