Serum levetiracetam concentrations and adverse events after multiple dose extended release levetiracetam administration to healthy cats

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Multiple dose administration of antiepileptic drugs to cats presents a challenge for owners. Extended release levetiracetam (XRL) has once daily recommended dosing interval, but multiple dose administration of XRL has not been evaluated in cats.


Evaluate serum levetiracetam concentrations and adverse clinical effects after 11 days of once daily XRL administration to healthy cats.


Nine healthy privately owned cats, body weight ≥ 5 kg


Extended release levetiracetam (500 mg/cat) was administered PO q24h for 10 days. On day 11, blood was collected at trough, 4, 6, and 8 hours after tablet administration. Owners maintained records of adverse effects throughout study. Levetiracetam was quantitated in serum using immunoassay validated in cats.


Median dose 94.3 mg/kg q24h. Median (range) trough, 4, 6, and 8 hour serum levetiracetam concentrations were 7.0 (2.3–14.1), 82.6 (7.8–125.3), 92.3 (13.3–97.3), and 72 (22.8–96.4) μg/mL, respectively. Peak was not observed in 4 cats because of missed samples (n = 2) and failure to reach maximal concentration (Cmax) by 8 hours (n = 2). Median time of maximal concentration (Tmax) for the remaining 5 cats 5.2 (range 4–6) hours. Adverse effects were minimal and included ataxia (n = 1), sedation (n = 1), and vomiting or regurgitation (n = 1). All signs resolved without dose adjustment or additional treatment.

Conclusions and Clinical Importance

Mean trough serum levetiracetam concentrations were ≥5 μg/mL and adverse effects were minimal throughout dosing period, indicating that the drug was well tolerated. Once daily XRL (500 mg/cat) administration may provide an easier alternative to 3 times daily dosing of intermediate-release levetiracetam for epileptic cats.

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