In vitro drug-drug interactions of budesonide: inhibition and induction of transporters and cytochrome P450 enzymes.

1. Budesonide is a glucocorticoid used in the treatment of several respiratory and gastrointestinal inflammatory diseases. Glucocorticoids have been demonstrated to induce cytochrome P450 (CYP) 3A and the efflux transporter P-glycoprotein (P-gp). This study aimed to evaluate the potential of budesonide to act as a perpetrator or a victim of transporter- or CYP-mediated drug-drug interactions (DDIs). 2. In vitro studies were conducted for P-gp, breast cancer resistance protein and organic anion and cation transporters (OATP1B1, OATP1B3, OAT1, OAT3, OCT2) in transporter-transfected cells. Changes in mRNA expression in human hepatocytes and enzyme activity in human liver microsomes by budesonide were determined for CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A. 3. The data indicated that budesonide is a substrate of P-gp but is not a substrate or an inhibitor of the other transporters investigated. Budesonide is neither an inducer nor an inhibitor of major CYP enzymes. The effect of P-gp on budesonide disposition is anticipated to be low owing to CYP3A-mediated clearance. 4. Collectively, our data indicate there is a low risk of budesonide perpetrating clinical DDIs mediated by the transporters or CYPs studied.