Effects of Age and Sex on the Single-Dose Pharmacokinetics and Pharmacodynamics of Apixaban

BACKGROUND AND OBJECTIVES: The effects of age and sex on apixaban pharmacokinetics and pharmacodynamics were studied. METHODS: This was an open-label, single-dose, 2 × 2 factorial study. Healthy young (aged 18–40 years) and elderly (aged ≥65 years) male and female subjects received a single oral 20 mg dose of apixaban. Blood and urine samples were collected for pharmacokinetic and pharmacodynamic (blood only) analyses. Subjects were monitored for adverse events throughout the study. RESULTS: Seventy-nine subjects were enrolled into four groups: young males (n = 20), elderly males (n = 20), young females (n = 20) and elderly females (n = 19). Age did not affect the maximum observed plasma concentration (C (max)). The mean area under the concentration–time curve from time zero extrapolated to infinite time (AUC(∞)) was 32 % greater in elderly subjects than in young subjects. The mean C (max) and AUC(∞) values were 18 and 15 % higher, respectively, in females than in males. The time course of the mean international normalized ratio (INR), modified prothrombin time (mPT) and anti-Xa activity tracked the apixaban concentration–time curve. All three pharmacodynamic measures exhibited a positive linear correlation with the plasma apixaban concentration. Differences in the mean INR, mPT and anti-Xa activity between age and sex groups were small (<15 % at the maximum mean values) and were generally related to pharmacokinetic differences. However, anti-Xa activity demonstrated less variability than the INR or mPT, and may have utility as a bioassay for apixaban. Apixaban was well tolerated, with no serious adverse events. CONCLUSION: There were no clinically meaningful age- or sex-related differences in the pharmacokinetics and pharmacodynamics of apixaban that would require dose modification on the basis of age or sex alone.