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

BACKGROUND: 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. OBJECTIVE: Evaluate serum levetiracetam concentrations and adverse clinical effects after 11 days of once daily XRL administration to healthy cats. ANIMALS: Nine healthy privately owned cats, body weight ≥ 5 kg METHODS: 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. RESULTS: 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 (C (max)) by 8 hours (n = 2). Median time of maximal concentration (T (max)) 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.