title: Measurement of Anti-Factor Xa Activity in Patients on Apixaban for Non-Valvular Atrial Fibrillation.
abstract: BACKGROUND
  Chromogenic anti-factor Xa activity (AXA) assay is reported to be the most appropriate method to measure the pharmacodynamics of apixaban, but the distribution of AXA in non-valvular atrial fibrillation (NVAF) patients on apixaban therapy has not been fully elucidated.
  
  
  RESULTS
  Steady-state trough and peak AXA were measured in 124 NVAF patients taking apixaban. In 25 patients, baseline, first peak, and trough AXA were also examined, and were 0.01±0.02 IU/ml, 0.83±0.43 IU/ml, and 0.34±0.17 IU/ml, respectively. First trough AXA was significantly lower than steady-state trough AXA, although it was significantly higher than baseline (P<0.0001). Similarly, first peak AXA was significantly lower than steady-state peak AXA (P<0.0001). In 124 patients, steady-state peak AXA was significantly higher in the 5-mg b.i.d. group than in the 2.5-mg b.i.d. group (2.05±0.73 IU/ml vs. 1.51±0.65 IU/ml, respectively; P<0.001), although there was no significant difference in trough AXA. Other than dose, age and serum creatinine were significantly related to both trough and peak AXA.
  
  
  CONCLUSIONS
  The distribution of AXA in Japanese NVAF patients on apixaban therapy in daily clinical practice both in the acute and steady-state phase was measured. In patients taking apixaban, measurement of AXA clearly showed the pharmacodynamic profile of this drug.
authors.affiliation: Division of Cardiology, Tosei General Hospital.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Osanai
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Ajioka
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Masutomi
authors.forename: Tasuku
authors.initials: T
authors.lastname: Kuwayama
authors.forename: Sota
authors.initials: S
authors.lastname: Ishihama
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Sakamato
authors.forename: Naoya
authors.initials: N
authors.lastname: Otaka
authors.forename: Teruhiro
authors.initials: T
authors.lastname: Sakaguchi
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Inoue
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kanbara
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Nakashima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Asano
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Sakai
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001281:Atrial Fibrillation / Q000097:blood / Q000188:drug therapy; D004305:Dose-Response Relationship, Drug; D065427:Factor Xa Inhibitors / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D011720:Pyrazoles / Q000008:administration & dosage / Q000493:pharmacokinetics; D011728:Pyridones / Q000008:administration & dosage / Q000493:pharmacokinetics
chemical_list: D065427:Factor Xa Inhibitors; D011720:Pyrazoles; D011728:Pyridones; C522181:apixaban