[Clinical Pharmacometrics for Rational Drug Treatment]

Pharmacometrics is the mathematical study of pharmacokinetics, disease progression, and clinical outcomes. One objective of pharmacometrics is to facilitate rational drug treatment in patients, also termed clinical pharmacometrics. In this review, our clinical pharmacometric studies conducted over the last 10 years are discussed. Population pharmacokinetic analysis using therapeutic monitoring data for levetiracetam revealed that oral clearance allometrically scaled to both body weight and estimated glomerular filtration rate can accurately predict clinical data from patients of various ages (pediatric to elderly) with varying renal function. Dosage adjustments based on renal function in the package information are effective in controlling the trough and peak concentrations in similar ranges. In addition, a retrospective pharmacokinetic and pharmacodynamic study revealed that the efficacy of low-dose clobazam therapy was significantly influenced by CYP2C19 polymorphisms. Pharmacokinetic and pharmacodynamic models were successfully built using electronic medical information to explain retrospective international normalized ratio values of prothrombin time before and after catheter ablation in warfarin-treated patients. Simulation studies suggest that more than 20 mg of vitamin K₂ is unnecessary in the preoperative period of catheter ablation. A physiologically based pharmacokinetic model adapted to tacrolimus pharmacokinetic data in patients who underwent living-donor liver transplantation was constructed, and clarified that oral clearance of this drug was affected by CYP3A5 genotypes in both the liver and intestine to the same extent. In conclusion, pharmacometrics is a useful methodology for individualized and optimized drug therapy.