title: Simultaneous quantification of levetiracetam and gabapentin in plasma by ultra-pressure liquid chromatography coupled with tandem mass spectrometry detection.
abstract: BACKGROUND
  Gabapentin (Neurontin) and levetiracetam (Keppra) are anticonvulsants with novel structures and suggested therapeutic ranges of 2-10 mg/L and 6-20 mg/L, respectively. Gabapentin is also used extensively to manage neuropathic pain, and for this indication, wherein higher doses are prescribed, plasma concentrations of 15-30 mg/L are typical.
  
  
  OBJECTIVE
  Here, we describe a simple rapid assay to support therapeutic drug monitoring of gabapentin and levetiracetam in plasma by ultra-pressure liquid chromatography couples to tandem mass spectrometry (UPLC-MS/MS) detection.
  
  
  METHODS
  After the addition of internal standard and protein precipitation of patient plasma with methanol:acetonitrile in a 50:50 ratio, 1 μL of supernatant sample is injected onto an Acquity UPLC HSS T3, 1.8 μm, 2.1 × 50 mm (Waters) column. Elution occurs using a linear gradient of acetonitrile and water, each having 0.1% formic acid added. The column is eluted into a Waters Acquity UPLC TQD, operating in a positive mode to detect gabapentin at transition 172.18 > 154.11, levetiracetam at 171.11 > 126, and internal standard (3-amino-2-naphthoic acid) at 188.06 > 170. Secondary transitions for each analyte are also monitored for gabapentin at 172.18 > 137.06, levetiracetam at 171.11 > 154, and internal standard at 188.06 > 115. Runtime is 1.5 minutes per injection with baseline resolved chromatographic separation.
  
  
  RESULTS
  The analytical measurement ranges were 1-150 mg/L for gabapentin and for levetiracetam. Intra-assay imprecision by the coefficient of variance (CV) was less than 8% and interassay CV was less than 5% for both analytes, at 4 different concentrations. Results obtained from patient samples were compared with results generated by established high-performance liquid chromatography-UV methods with the following regression statistics: y = 1.12x - 0.77, r = 0.996, Sy, x = 0.89, and n = 29 for gabapentin and y = 0.991x + 0.70, r = 0.997, Sy, x = 2.24, and n = 30 for levetiracetam. No analytical interferences were identified.
  
  
  CONCLUSIONS
  : In summary, a simple reliable UPLC-MS/MS method was developed and validated for routine clinical monitoring of gabapentin and levetiracetam.
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, ARUP Laboratories, Salt Lake City, Utah, USA. juenkejm@aruplab.com
authors.forename: JoEtta M
authors.initials: JM
authors.lastname: Juenke
authors.forename: Paul I
authors.initials: PI
authors.lastname: Brown
authors.forename: Kamisha L
authors.initials: KL
authors.lastname: Johnson-Davis
authors.forename: Gwendolyn A
authors.initials: GA
authors.lastname: McMillin
mesh_terms: D000588:Amines / Q000097:blood* / Q000737:chemistry; D000927:Anticonvulsants / Q000097:blood* / Q000737:chemistry; D002853:Chromatography, Liquid / Q000379:methods*; D003509:Cyclohexanecarboxylic Acids / Q000097:blood* / Q000737:chemistry; D016903:Drug Monitoring / Q000379:methods*; D000077206:Gabapentin; D006801:Humans; D000077287:Levetiracetam; D010889:Piracetam / Q000031:analogs & derivatives* / Q000097:blood / Q000737:chemistry; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*; D005680:gamma-Aminobutyric Acid / Q000097:blood* / Q000737:chemistry
chemical_list: D000588:Amines; D000927:Anticonvulsants; D003509:Cyclohexanecarboxylic Acids; D000077287:Levetiracetam; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin; D010889:Piracetam