Pharmacokinetics of Oral Gabapentin Alone or Co-administered with Meloxicam in Ruminant Beef Calves

Gabapentin is a γ-aminobutyric acid (GABA) analogue indicated for treatment of neuropathic pain. This study determined the pharmacokinetics of oral (PO) gabapentin alone or in combination with meloxicam in ruminant calves. Gabapentin capsules at 10mg/kg or gabapentin powder (from capsules at 15mg/kg) and meloxicam tablets (0.5mg/kg) were administered PO to six beef calves. Plasma drug concentrations were determined over 48h post-administration by liquid chromatography/mass spectrometry followed by non-compartmental pharmacokinetic analysis. The mean (± standard deviation, SD) C(max), T(max) and elimination half-life (t(½)λz) for gabapentin (10mg/kg) alone was 2.97 ± 0.40μg/mL, 9.33 ± 2.73h and 11.02 ± 3.68h, respectively. The mean (± SD) C(max), T(max) and t(½)λz for gabapentin (15mg/kg) co-administered with meloxicam was 3.57±1.04μg/mL, 7.33 ± 1.63h and 8.12±2.11h, respectively. The mean (±SD) C(max), T(max) and t(½)λz for meloxicam was 2.11± 0.19μg/mL, 11.67 ± 3.44h and 20.47 ± 9.22h, respectively. Plasma gabapentin concentrations >2μg/mL were maintained for up to 15h and meloxicam concentrations >0.2μg/mL for up to 48h. The pharmacokinetic profile of oral gabapentin and meloxicam supported clinical evaluation of these compounds for management of neuropathic pain in cattle.