Pharmacokinetics of gabapentin in cats

Objective-To determine the pharmacokinetics of gabapentin in cats after IV and oral administration. Animals-6 healthy female adult domestic shorthair cats. Procedures-Gabapentin was administered IV (4 mg/kg) or orally (10 mg/kg) in a crossover randomized design. Blood samples were obtained immediately before gabapentin administration and at various times up to 960 minutes after IV administration or up to 1,440 minutes after oral administration. Blood samples were immediately transferred to tubes that contained EDTA and were centrifuged at 4 C. Plasma was harvested and stored at 20 C until analysis. Plasma concentrations of gabapentin were determined by use of liquid chromatography mass spectrometry. Gabapentin concentration-time data were fit to compartment models. Results-A 3-compartment model with elimination from the central compartment best described the disposition of gabapentin administered IV to cats, but a 1-compartment model best described the disposition of gabapentin administered orally to cats. After IV administration, the mean +/- SEM apparent volume of the central compartment, apparent volume of distribution at steady state, and clearance and the harmonic mean jackknife pseudo-SD for terminal half-life were 90.4 +/- 11.3 mL/kg, 650 +/- 14 mL/kg, 3 +/- 0.2 mL/min/kg, and 170 +/- 21 minutes, respectively. Mean +/- SD systemic availability and harmonic mean +/- jackknife pseudo-SD terminal half-life after oral administration were 88.7 +/- 11.1% and 177 +/- 25 minutes, respectively. Conclusions and Clinical Relevance-The disposition of gabapentin in cats was characterized by a small volume of distribution and a low clearance. (Am J Vet Res 2010;71:817-821)