Dược Động Học :
▧ Absorption :
Apixaban is absorbed in the stomach and small intestine. For doses up to 10 mg, the absolute bioavailability is about 50%. For oral administration, absorption is not affected by the presence of food, and it takes about 3-4 hours to achieve maximum plasma concentrations. For large oral doses equal or greater than 25 mg, absorption is dissolution limited and bioavailability is decreased. Most of the absorption occurs in the distal small intestine and the ascending colon.
▧ Volume of Distribution :
The steady state volume of distribution is 21 L.
▧ Protein binding :
Apixaban is about 87% plasma protein bound.
▧ Metabolism :
Apixaban mainly undergoes o-demethylation and hydroxylation to metabolites. The major site of biotransformation is at the 3-oxopiperidinyl moiety. The main enzyme responsible for metabolism is CYP3A4/5 while CYP1A2, 2C8, 2C9, 2C19, and 2J2 are minor metabolic enzymes. There are no active metabolites and unchanged apixaban is the primary circulating entity.
▧ Route of Elimination :
25% of the administered dose is eliminated in the feces and urine. For elimination in the feces, it is excreted by the intestine and bile to the feces.
▧ Half Life :
If administered orally, the half life is 12 hours (due to prolonged absorption). If administerd by I.V., the half-life is about 5 hours.
▧ Clearance :
About 27% of total apixaban is renally cleared.