Effect of Coadministered Ketoconazole, a Strong Cytochrome P450 3A4 Enzyme Inhibitor, on the Pharmacokinetics of Ciclesonide and its Active Metabolite Desisobutyryl-Ciclesonide

Background and objectives: Cytochrome P450 (CYP) 3A4 isoenzyme has been identified in vitro as the key enzyme to metabolize desisobutyryl-ciclesonide (des-CIC), the pharmacologically active metabolite of the inhaled corticosteroid ciclesonide. This pharmacokinetic drug-drug interaction study was conducted to confirm this major metabolic pathway in vivo by using the strong CYP3A4 inhibitor ketoconazole, and to assess the effect of ketoconazole on the pharmacokinetics of ciclesonide and des-CIC.