The half-life of levetiracetam (LEV) in cats approximates 3 hours, prompting the need for an extended release LEV (ER-LEV) formulation. The purpose of this study was to describe and compare pharmacokinetics of ER-LEV in both plasma and CSF in cats after a single dose of approved and compounded ER-LEV.
Using a non-randomized cross-over design, nine clinically healthy cats received a single dose of 500 mg of approved ER-LEV PO. Thirteen blood and 1-2 CSF samples were collected over 24 hours. After a one-week washout period, the study was repeated with a single oral dose of 500 mg compounded ER-LEV. LEV was quantitated by immunoassay. Plasma and pooled CSF LEV concentrations versus time data were subjected to noncompartmental pharmacokinetic analysis and data were compared between formulations using a paired t-test.
Regardless of formulation, CSF LEV closely mimicked plasma concentrations. Significant differences (P < 0.05) between formulations were limited to plasma Cmax (ug/mL) (approved 126 +/- 33; compounded 169 +/- 51) and tmax (approved 5.1 +/- 1.6; compounded 3.1 +/- 1.5). With a half-life of 12.6 +/- 1.6 hours and 12.7 +/- 2.0 for approved and compounded, respectively, both formulations maintained concentrations above the human therapeutic reference interval for at least 12 hours.
This study demonstrates that both approved and compounded ER-LEV maintains human therapeutic LEV concentrations in healthy cats 12 hours after oral administration, supporting 12-hour dosing intervals. This study also demonstrates that plasma LEV monitoring can be used as an accurate representation of CSF LEV concentrations in cats.
Resident of Neurology & Neurosurgery
Auburn University College of Veterinary Medicine
Thursday, June 14
10:45 AM – 11:00 AM
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