Population pharmacokinetics and dose-response relationship of levetiracetam in adult patients with epilepsy.

Levetiracetam (LEV) is commonly used as a mono- or adjunctive therapy for treating patients with partial and generalized epilepsy. This study aimed to develop a population pharmacokinetic (PK) model of LEV, based on sparse data, and to explore LEV efficacy relative to its PK properties in patients with epilepsy. We included 483 LEV concentrations from 425 patients with epilepsy that received multiple oral LEV doses. We performed a population PK analysis, implemented in NONMEM (version 7.2). In addition, we explored the relationships between seizure control and PK variables (i.e., LEV dose, trough concentration, and the number of concomitant anti-epileptic drugs). LEV concentration-time profiles were adequately described with a one-compartment, open linear model, with first-order absorption, and additive residual error. The typical population estimates of the apparent clearance (CL/F) and the volume of distribution (V/F) were 3.9L/h and 65.3L, respectively. Body weight was a significant covariate for CL/F and V/F; the estimated glomerular filtration rate only significantly affected CL/F; and concomitant intake of other anti-epileptic drugs did not significantly affect either parameter. A cumulative percentage analysis revealed that over 95% of patients that remained seizure-free received LEV doses of 2000mg/day or lower. LEV trough concentrations were not significantly different between seizure-free and seizure groups, for each LEV dose. In conclusion, we successfully developed a population PK model of LEV, which enabled investigation of LEV efficacy, relative to its PK properties. The findings in this study can be utilized to optimize LEV dosing regimens in clinical practice.