Drug Interaction Report

ADJUST DOSING INTERVAL: Food may interfere with the absorption of esomeprazole. The manufacturer reports that the area under the concentration-time curve for esomeprazole following a single 40 mg dose was 33% to 53% lower when administered after food intake as opposed to during fasting conditions.

MANAGEMENT: Esomeprazole should be taken at least one hour before meals. When administered to patients receiving continuous enteral nutrition, some experts recommend that the tube feeding should be interrupted for at least 1 hour before and 1 hour after the dose of esomeprazole is given.

MONITOR: Grapefruit juice may increase the plasma concentrations of orally administered drugs that are substrates of the CYP450 3A4 isoenzyme, such as cobimetinib. However, the interaction seems to affect primarily those drugs that undergo significant presystemic metabolism by CYP450 3A4 (i.e., drugs with low oral bioavailability), presumably due to the fact that grapefruit juice inhibits primarily intestinal rather than hepatic CYP450 3A4. Because pharmacokinetic interactions involving grapefruit juice are often subject to a high degree of interpatient variability, the extent to which a given patient may be affected is difficult to predict.

MANAGEMENT: Patients who regularly consume grapefruit or grapefruit juice should be monitored for adverse effects and altered plasma concentrations of cobimetinib. Grapefruit and grapefruit juice should be avoided if an interaction is suspected. Orange juice is not expected to interact with these drugs.