Pharmacokinetics of the Oral Direct Renin Inhibitor Aliskiren in Combination With Digoxin, Atorvastatin, and Ketoconazole in Healthy Subjects: The Role of P-Glycoprotein in the Disposition of Aliskiren

This study investigated the potential pharmacokinetic interaction between the direct renin inhibitor aliskiren and modulators of P-glycoprotein and cytochrome P450 3A4 (CYP3A4). Aliskiren stimulated in vitro P-glycoprotein ATPase activity in recombinant baculovirus infected Sf9 cells with high affinity (K-m 2.1 mu mol/L) and was transported by organic anion -transporting peptide OATP2B1-expressing HEK293 cells with moderate affinity (K-m 72 mu mol/L). Three open-label, multiple-dose studies in healthy subjects investigated the pharmacokinetic interactions between aliskiren 300 mg and digoxin 0.25 mg (n = 22), atorvastatin 80 mg (n = 21), or ketoconazole 200 mg bid (n = 21). Coadministration with aliskiren resulted in changes of <30% in AUC(tau) and C-max,C-ss of digoxin, atorvastatin, o-hydroxy-atorvastatin, and phydroxy-atorvastatin, indicating no clinically significant interaction with P-glycoprotein or CYP3A4 substrates. Aliskiren AUC(tau) was significantly increased by coadministration with atorvastatin (by 47%, P <.001) or ketoconazole (by 76%, P <.001) through mechanisms most likely involving transporters such as P-gycoprotein and organic anion -transporting peptide and possibly through metabolic pathways such as CYP3A4 in the gut wall. These results indicate that aliskiren is a substrate for but not an inhibitor of P-glycoprotein. On the basis of the small changes in exposure to digoxin and atorvastatin and the <2-fold increase in exposure to aliskiren during coadministration with atorvastatin and ketoconazole, the authors conclude that the potential for clinically relevant drug interactions between aliskiren and these substrates and/or inhibitors of P-glycoprotein/CPY3A4/OATP is low.