CO-ADMINISTERATION WITH STRONG CYP3A INHIBITORS (E.G., KETOCONAZOLE), THE DOSE SHOULD BE REDUCED TO 150 MG TWICE-A-WEEK. THE DOSE OF IVACAFTOR SHOULD BE REDUCED TO 150 MG ONCE DAILY WHEN CO-ADMINISTERED WITH MODERATE CYP3A INHIBITORS (E.G., FLUCONAZOLE). FOOD CONTAINING GRAPEFRUIT OR SEVILLE ORANGES SHOULD BE AVOIDED.
COADMINISTRATION WITH STRONG CYP3A INDUCERS, SUCH AS RIFAMPIN, RIFABUTIN, PHENOBARBITAL, CARBAMAZEPINE, PHENYTOIN, AND ST. JOHN'S WORT IS NOT RECOMMENDED SINCE THEY REDUCE IVACAFTOR CONC. BY 9 FOLDS.
IVACAFTOR IS A WEAK INHIBITION OF CYP3A AND P-GP SUBSTRATES, SO CO- ADMINISTRATION MAY INCREASE OR PROLONG THERAPEUTIC EFFECT AND ADVERSE EVENTS OF MIDAZOLAM, DIGOXIN, CYCLOSPORINE, AND TACROLIMUS.