Drug Interactions between brigatinib and Lanoxin

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of brigatinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Itraconazole, a potent CYP450 3A4 inhibitor, has been shown to double brigatinib systemic exposure (AUC) in healthy volunteers. Increased exposure to brigatinib may increase the risk of adverse effects such as nausea, vomiting, diarrhea, hypertension, bradycardia, hyperglycemia, visual disturbances, lymphopenia, anemia, and elevations in pancreatic enzymes and creatine phosphokinase.

Food does not significantly affect the oral bioavailability of brigatinib. When brigatinib was administered to healthy volunteers after a high-fat meal (920 calories; 59 g fat, 58 g carbohydrates, 40 g proteins), brigatinib peak plasma concentration (Cmax) decreased by 13% and systemic exposure (AUC) did not change compared to administration after overnight fasting.

MANAGEMENT: Brigatinib may be taken with or without food. Patients should avoid consumption of grapefruit and grapefruit juice during treatment with brigatinib.

Administration of digoxin with a high-fiber meal has been shown to decrease its bioavailability by almost 20%. Fiber can sequester up to 45% of the drug when given orally. Patients should be advised to maintain a regular diet without significant fluctuation in fiber intake while digoxin is being titrated.

Grapefruit juice may modestly increase the plasma concentrations of digoxin. The mechanism is increased absorption of digoxin due to mild inhibition of intestinal P-glycoprotein by certain compounds present in grapefruits. In 12 healthy volunteers, administration of grapefruit juice with and 30 minutes before, as well as 3.5, 7.5, and 11.5 hours after a single digoxin dose (0.5 mg) increased the mean area under the plasma concentration-time curve (AUC) of digoxin by just 9% compared to administration with water. Moreover, P-glycoprotein genetic polymorphism does not appear to influence the magnitude of the effects of grapefruit juice on digoxin. Thus, the interaction is unlikely to be of clinical significance.