Validation of a High-throughput Screening and Quantification Method for the Determination of Gabapentinoids in Blood Using a Combination of LC-TOF-MS and LC-MS-MS

Gabapentinoids such as gabapentin (GP) and pregabalin (PGL) have been used to treat a wide range of neurological and psychiatric disorders. In recent years, there has been an increasing awareness of GP and PGL misuse among individuals with a history of polysubstance use. Both GP and PGL are understood to potentiate the effects of opioids, with fatalities involving GP and PGL being reported with increasing frequency. An efficient procedure was developed to screen and quantitate GP and PGL in blood samples using a combination of liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) and liquid chromatography tandem mass spectrometry (LC-MS-MS). The developed LC-MS-MS method was linear from 0.5-50 mg/L, with a limit of detection (LOD) of 0.1 mg/L for GP and PGL. An LOD of 0.5 mg/L was determined for both analytes on the LC-TOF-MS screen. A total of 1,091 blood specimens were subjected to a protein crash with methanol, in the presence of deuterated internal standards, PGL-d(6) and GP-d(10), to minimize the effects of varying matrix conditions. Specimens tested included both post-mortem blood and preserved blood specimens collected for the purposes of investigating drug-impaired driving and suspected drug-facilitated crimes. Of the total of specimens tested, 101 (9.3%) screened positive using the developed LC-TOF-MS method for GP while only 13 (1.2%) blood specimens screened positive for PGL. All (100%) of the cases that screened positive for GP and PGL were confirmed positive by LC-MS-MS. Blood concentrations of GP and PGL ranged from <0.5 to 215 mg/L and from <0.5 to 32 mg/L, respectively. Of the blood specimens that had previously screened negative by LC-TOF-MS, 10%(N = 100) were randomly selected and tested by LC-MS-MS with 100% confirmed negative for GP and PGL. The developed methods provide a fast and reliable high-throughput screening and confirmation testing strategy for the detection of GP and PGL in blood specimens.