Pharmacokinetics of Single Oral Dose Extended‐Release Levetiracetam in Healthy Cats

BACKGROUND Repeated PO dosing of anti-epileptic drugs may contribute to poor compliance in treated cats. Intermediate-release levetiracetam has been used safely in cats, but must be given q8h to maintain serum concentrations in the therapeutic interval for humans (5-45 μg/mL). Approved extended-release levetiracetam (XRL) for human use may require less frequent dosing, but the large dosing unit has limited its use in cats. HYPOTHESES In healthy cats, serum levetiracetam concentration will remain above 5 μg/mL for at least 24 hours after administration of a single dose of XRL PO and will be well tolerated. ANIMALS 7 healthy cats. METHODS Extended-release levetiracetam (500 mg) was administered PO. Blood was collected and neurologic examination findings recorded at scheduled times over 30 hours. Serum levetiracetam concentration was quantitated by an immunoassay validated in cats. Data were subjected to noncompartmental analysis. Descriptive statistics were reported. RESULTS The median dosage of 86.2 mg/kg, (range, 80-94.3) achieved a mean maximum concentration (Cmax ) of 89.8 ± 25.8 μg/mL at 4.9 ±1.57 hours. Serum levetiracetam was >5 μg/mL in all cats by 90 minutes. Mean concentrations were 43.7 ± 18.4 and 4.9 ± 3.4 μg/mL at 12 and 24 hours, respectively. The half-life was 4.1 ± 1.0 hours. The drug was well tolerated. CONCLUSIONS AND CLINICAL IMPORTANCE A single 500 mg PO dose of XRL safely maintained serum levetiracetam concentration ≥5 μg/mL in healthy cats for at least 21 hours. Clinical efficacy studies in epileptic cats receiving XRL are indicated; however, monitoring should be implemented for individual cats.