Population pharmacokinetics of a single oral dose of gabapentin identifies rapid plasma clearance in rehabilitated Pacific harbor seal pups (Phoca vitulina richardii)

Determine the pharmacokinetic parameters of a single dose of gabapentin administered orally in healthy weaned Pacific harbor seal (HS) pups (Phoca vitulina richardii). In the spring of 2023, rehabilitated HS pups were enrolled in this pharmacokinetic study. Seals were administered 10 mg/kg of gabapentin orally in a fish. A sparse sampling model was employed to collect blood samples from 0.25 to 48 hours after drug administration. Plasma drug concentrations were determined using liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were determined using noncompartmental analysis for sparse data. 15 HSs were included in this study. The mean peak plasma concentration was 7,669.4 ng/mL, the mean time to peak plasma concentration was 1 hour, the mean area under the concentration-versus-time curve from time 0 to infinity was 23,811.8 h·ng/mL, and the mean terminal half-life was 1.9 hours. No adverse effects were observed in any HSs. The plasma concentration of gabapentin that confers analgesia is not known in veterinary species. During this study, mean gabapentin concentrations exceeded the concentration estimated to treat neuropathic pain in humans only at 1 hour. Gabapentin was rapidly absorbed and eliminated in HSs, indicating that higher dosages and/or frequent dosing of gabapentin may be needed to maintain targeted plasma concentrations in young HSs. Additional studies to investigate the clinical efficacy of gabapentin in veterinary species are warranted, and clinical discretion should be used when applying these results to patients outside of the specific demographic group studied here.