A sensitive LC-MS/MS method for the quantitation of oxycodone, noroxycodone, 6α-oxycodol, 6β-oxycodol, oxymorphone,...

The objective of this study was to develop and validate a highly sensitive method for the detection of oxycodone, noroxycodone, 6β-oxycodol, 6α-oxycodol, oxymorphone, and noroxymorphone in blood by liquid chromatography tandem mass spectrometry. The analytes were extracted from blood (0.5 mL) using Bond Elut Certify Solid Phase Extraction columns, evaporated to dryness and reconstituted before analysis was performed on an Acquity UPLC® I-class coupled to a Waters Xevo TQD. Academy Standards Board Standard Practices for Method Development in Forensic Toxicology were used for the validation of this method. The limit of quantitation for all analytes was established at 0.5 ng/mL. Calibration range for noroxymorphone, oxymorphone, 6α-oxycodol and 6β-oxycodol was 0.5-25 ng/mL and 0.5-100 ng/mL for noroxycodone and oxycodone. Precision (2.90-17.3%) and bias studies resulted in a ±15% deviation. There were no interferences observed from internal standard, matrix, or common drugs of abuse. Stability of all analytes at two concentrations at 24, 48, and 72 h in the autosampler did not exceed ±20% difference from the initial T₀. Dilution integrity at a ten-fold dilution was acceptable as analyte concentrations ranged between (±18%) of the target concentration. Once validated, the method was used in a pilot dosing study of one male subject after taking a 10 mg immediate release tablet of oxycodone. Blood samples were collected at 0.25, 0.50, 0.75, 1.0, 1.5, 2, 3, 4, 5, 6, 8, 9, and 24 h after ingestion. Oxycodone and noroxycodone both reached T_max at 1.5 h and had C_max values of 25.9 and 12.8 ng/mL, respectively. Oxycodone, 6α-oxycodol, and 6β-oxycodol were detectable up to 9 h, while noroxymorphone and noroxycodone were still detected at 24 h.