Drug Interaction Report

Coadministration with inhibitors of CYP450 3A4 may increase the plasma concentrations of modafinil (the racemate) and armodafinil (the R-enantiomer), which are both partially metabolized by the isoenzyme. Conversely, the plasma levels of some of these inhibitors may decrease, since many of them are also substrates of CYP450 3A4, and modafinil and armodafinil have been found to be modest inducers of CYP450 3A4. The clinical significance of this potential interaction is unknown. Clinical monitoring for altered effects of modafinil and armodafinil as well as the CYP450 3A4 inhibitor may be appropriate following addition or withdrawal of one or the other drug. Dose adjustments may be required if an interaction is suspected.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of crizotinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. Because crizotinib is associated with concentration-dependent prolongation of the QT interval, increased levels may potentiate the risk of ventricular arrhythmias such as torsade de pointes and sudden death.

Food has no significant effect on the gastrointestinal absorption of crizotinib. According to the product labeling, a high-fat meal reduced crizotinib peak plasma concentration (Cmax) and systemic exposure (AUC) by approximately 14%.

MANAGEMENT: Patients treated with crizotinib should avoid consumption of grapefruit, grapefruit juice, and any supplement containing grapefruit extract. Crizotinib may be taken without regards to food.

Administration with food may delay the absorption of modafinil (the racemate) and armodafinil (the R-enantiomer) without significantly affecting their overall bioavailability. According to the product labeling, modafinil's absorption may be delayed by approximately one hour if taken with food. Similarly, the time to reach peak plasma concentration (Tmax) of armodafinil may be delayed by approximately 2 to 4 hours in the fed state.