Objective: Apixaban is a substrate of cytochrome P450 3A4 (CYP3A4) and P-glycoprotein. The effects of rifampin, a strong inducer of CYP3A4 and P-glycoprotein, on the pharmacokinetics of oral and intravenous apixaban were evaluated in an open-label, randomized, sequential crossover study.
Methods: Twenty healthy participants received single doses of apixaban 5 mg intravenously on day 1 and 10 mg orally on day 3, followed by rifampin 600 mg once daily on days 5-15. Finally, participants received single doses of apixaban 5 mg intravenously and 10 mg orally separately on days 12 and 14 in one of two randomized sequences.
Results: Apixaban, given intravenously and orally, was safe and well tolerated when administered in the presence and absence of rifampin. Apixaban absolute oral bioavailability was 49 % when administered alone and 39 % following induction by rifampin. Rifampin reduced apixaban area under the plasma concentration-time curve from time zero to infinity (AUC∞) by 39 % after intravenous administration and by 54 % after oral administration. Rifampin induction increased mean clearance by 1.6-fold for intravenous apixaban and mean apparent clearance by 2.1-fold for oral apixaban, indicating rifampin affected both pre-systemic and systemic apixaban elimination pathways.
Conclusion: Co-administration of apixaban with rifampin reduced apixaban exposure via both decreased bioavailability and increased systemic clearance.