Drug Interactions between osilodrostat and sodium phenylbutyrate / taurursodiol

MONITOR: Coadministration with inducers of CYP450 3A4 and/or 2B6 may decrease the plasma concentrations of osilodrostat, which is partially metabolized by these isoenzymes. According to the product labeling, multiple CYP450 isoenzymes (CYP450 3A4, 2B6, and 2D6) and UDP-glucuronosyltransferases contribute to osilodrostat metabolism, and no single pathway contributes greater than 25% to the total clearance. Some of the known CYP450 3A4 and 2B6 inducers also induce UDP-glucuronosyltransferases. Pharmacokinetic data for osilodrostat in combination with an inducer of one or more of these pathways have not been reported. Reduced therapeutic efficacy of osilodrostat may occur during coadministration. On the other hand, discontinuation of a CYP450 3A4 and/or 2B6 inducer during treatment with osilodrostat may result in increased osilodrostat plasma concentrations and increased risk of adverse effects such as hypocortisolism (which may lead to life-threatening adrenal insufficiency), QT prolongation (which may increase the risk of ventricular arrhythmias including torsade de pointes and sudden death), and elevated androgen and 11-deoxycorticosterone levels (the latter of which may activate mineralocorticoid receptors and cause hypokalemia, edema, and hypertension).

MANAGEMENT: The potential for diminished pharmacologic effects of osilodrostat should be considered during concomitant use of a CYP450 3A4 and/or 2B6 inducer. An increase in the dosage of osilodrostat may be required. Dosage adjustments should be based on clinical response and tolerance. Patients should have regular monitoring of 24-hour urine free cortisol and serum or plasma cortisol during treatment, as well as regular evaluations of their signs and symptoms. A reduction in dosage of osilodrostat may be required if the CYP450 3A4 and/or 2B6 inducer is discontinued during treatment with osilodrostat.