LC/MS/MS Analysis of Gabapentin, Benzodiazepines, and Opiates

Analysis of Gabapentin byLC/MS/MSWhat is Gabapentin?Gabapentin, an analog of the neurotransmitter GABA, is usedas an anticonvulsant in the treatment of epilepsy.It was approved by the FDA as an anti-seizure medication buthas many controversial off-label uses, such as in the treatmentof bipolar disorder, social anxiety disorder, obsessivecompulsivedisorder and insomnia.Gabapentin is also widely used as a pain reliever and was oneof the 50 most prescribed drugs in the United States in 2003due to its mild side-effect profile.Gabapentin may increase the effect of other drugs such asantidepressants, alcohol and pain relievers.Gabapentin StructureGabapentin Extraction MethodologyChemical structure of Gabapentin,(1-(aminomethyl)-cyclohexaneacetic acid)Methodology:The extraction of Gabapentin frombiological specimens is performedusing the principles of proteinprecipitation by acetonitrile (withouta clean up step) and detection byLC/MS/MS.Drugs to be determinedby this method:Gabapentin, Baclofen (IS),Carbinoxamine (Alternate IS)Instrumentation:Liquid Chromatograph withTandem Mass Spectrometer-MassSpectrometer DetectorColumn: Varian Pursuit Diphenyl(DP) Column Dimensions: 3um,50mm x 2.0mm Procedure:Accurately measure 1.0 ml ofstandard, quality control and casesamples.Add 10 ul of internal standard (finalconcentration = 10 ug/ml) to eachtube and vortex.Aliquot 50 ul of each standard,quality control and case sampleinto new tubes.Add 400 ul of acetonitrile to eachtube and vortex.Centrifuge for 10 minutes.Decant supernatant to a cleantube. Evaporate the supernatant todryness. Reconstitute the samples with 200ul of Methanol: Water (60:40).Vortex.Transfer the liquid to labeledAutoSampler vials with inserts.