title: Population model of the pharmacokinetics and pharmacodynamics of rivaroxaban--an oral, direct factor xa inhibitor--in healthy subjects.
abstract: OBJECTIVE
  Rivaroxaban (BAY 59-7939) is an oral, direct Factor Xa (FXa) inhibitor being developed for the prevention and treatment of thromboembolic disorders. This analysis aimed to define population models for the pharmacokinetics (PK) and pharmacodynamics (PD) ofrivaroxaban in healthy males.
  
  
  METHODS
  Non-linear, mixed-effect modeling was used to analyze rivaroxaban plasma concentration and PD data (FXa activity and clotting tests) from subjects in a phase I, multiple-ascending-dose study. Subjects received 5 mg rivaroxaban once, twice or three times daily, or 10, 20 or 30 mg rivaroxaban twice daily.
  
  
  RESULTS
  The population PK of rivaroxaban were well described by an oral, two-compartment model with first-order absorption and elimination from the central compartment. Population mean estimates for apparent oral clearance and volume of distribution for the central compartment were 9.2 1/h and 55 1, respectively, with moderate inter-individual variability (17.4% and 30.7%, respectively). Total volume of distribution for rivaroxaban at steady state was approximately 70 1. Residual (unexplained) variability was 25%. FXa activity correlated with rivaroxaban plasma concentrations following an inhibitory Emax model; prothrombin time (PT) and rivaroxaban plasma concentrations correlated with a linear model, with a slope of 4.6 s/(100 microg/1). Inter-individual variability was low for the correlation with PT. The models derived were used to define sampling windows for population PK/PD modeling in Phase II studies.
  
  
  CONCLUSIONS
  This analysis confirms that rivaroxaban has predictable, dose-proportional PK and PD. The linear correlation between rivaroxaban plasma concentrations and PT suggests that this test might be useful to assess rivaroxaban exposure in patients, if required.
authors.affiliation: Clinical Pharmacology, Pharmacometry, Bayer HealthCare AG, Wuppertal, Germany. wolfgang.mueck@bayerhealthcare.com
authors.forename: W
authors.initials: W
authors.lastname: Mueck
authors.forename: M
authors.initials: M
authors.lastname: Becka
authors.forename: D
authors.initials: D
authors.lastname: Kubitza
authors.forename: B
authors.initials: B
authors.lastname: Voith
authors.forename: M
authors.initials: M
authors.lastname: Zuehlsdorf
mesh_terms: D000293:Adolescent; D000328:Adult; D004305:Dose-Response Relationship, Drug; D065427:Factor Xa Inhibitors; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009025:Morpholines / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology*; D010314:Partial Thromboplastin Time; D011153:Population; D011517:Prothrombin Time; D000069552:Rivaroxaban; D013876:Thiophenes / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology*
chemical_list: D065427:Factor Xa Inhibitors; D009025:Morpholines; D013876:Thiophenes; D000069552:Rivaroxaban