MIFE is metabolized by CYP3A4 and is also an irreversible competitive inhibitor of CYP3A4 and, to a lesser extent, of CYPs 1A, 2B, 2D6 and 2E1. As MIFE binds CYP irreversibly and is slowly eliminated from the body, caution should be taken when MIFE is administered with drugs that are CYP3A4 substrates and have narrow therapeutic range[10].

Drug interactions of importance in the clinical setting that may alter the metabolism of MIFE include[10]:

• CYP3A4 inducers (glucocorticoids, macrolide antibiotics, rifampicin, carbamazepine, benzodiazepines, barbiturates, St. John’s wort).
• CYP3A4 inhibitors (cimetidine, ketoconazole, erythromycin, chloramphenicol, spironolactone, secobarbital, grapefruit juice).

MIFE has antiglucocorticoid activity; it may temporarily decrease the efficacy of corticosteroid therapy, including inhaled corticosteroids[10].

As for MISO, there is no known drug interactions. Oral ingestion with food or antacids may decrease oral bioavailability[10].