Levetiracetam Pharmacokinetics and Brain Uptake in a Lateral Fluid Percussion Injury Rat Model

Post-traumatic epilepsy (PTE) occurs in some patients after moderate/severe traumatic brain injury (TBI). Although there are no approved therapies to prevent epileptogenesis, levetiracetam (LEV) is commonly given for seizure prophylaxis due to its good safety profile. This led us to study LEV as part of the Epilepsy Bioinformatics Study for Antiepileptogenic Therapy (EpiBioS4Rx) Project. The objective of this work is to characterize the pharmacokinetics (PK) and brain uptake of LEV in naïve control rats and in the lateral fluid percussion injury (LFPI) rat model of TBI after either single intraperitoneal doses or a loading dose followed by a 7-day subcutaneous infusion. Sprague-Dawley rats were used as controls and for the LFPI model induced at the left parietal region using injury parameters optimized for moderate/severe TBI. Naïve and LFPI rats received either a bolus injection (intraperitoneal) or a bolus injection followed by subcutaneous infusion over 7 days. Blood and parietal cortical samples were collected at specified time points throughout the study. LEV concentrations in plasma and brain were measured using validated high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS) methods. Noncompartmental analysis and a naive-pooled compartmental PK modeling approach were used. Brain-to-plasma ratios ranged from 0.54 to 1.4 to 1. LEV concentrations were well fit by one-compartment, first-order absorption PK models with a clearance of 112 ml/h per kg and volume of distribution of 293 ml/kg. The single-dose pharmacokinetic data were used to guide dose selection for the longer-term studies, and target drug exposures were confirmed. Obtaining LEV PK information early in the screening phase allowed us to guide optimal treatment protocols in EpiBioS4Rx.