Drug Interactions between eltrombopag and pacritinib

GENERALLY AVOID: Theoretically, coadministration with grapefruit juice may increase the plasma concentrations of pacritinib, which is primarily metabolized by CYP450 3A4. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Inhibition of hepatic CYP450 3A4 may also contribute. The interaction has not been studied with grapefruit juice but has been reported for the potent CYP450 3A4 inhibitor, clarithromycin. In a clinical drug interaction study, a single dose of pacritinib (400 mg) was administered following treatment with clarithromycin (500 mg twice daily for 5 days). The peak plasma concentration (Cmax) and systemic exposure (AUC) of pacritinib increased by 30% and 80%, respectively, compared to pacritinib administered alone. Longer treatment with clarithromycin that results in maximal CYP450 3A4 inhibition may increase pacritinib exposure even higher. 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. Increased exposure to pacritinib may increase the risk of adverse effects such as diarrhea, thrombocytopenia, infection, and QT prolongation.

Pacritinib pharmacokinetics were not significantly affected when administered with a high-fat meal.

MANAGEMENT: Although clinical data are lacking, it may be advisable to avoid consumption of grapefruit or grapefruit juice during treatment with pacritinib. Pacritinib may be administered with or without food.

ADJUST DOSING INTERVAL: Food may reduce the oral bioavailability of eltrombopag. In healthy volunteers, a standard high-fat breakfast significantly decreased plasma eltrombopag peak plasma concentration (Cmax) by 65% and systemic exposure (AUC) by 59% and delayed Tmax by one hour. The calcium content of this meal may have also contributed to this decrease in exposure. In another study, adult subjects administered a single 25 mg dose of eltrombopag for oral suspension with a high-calcium, moderate-fat, moderate-calorie meal exhibited a 79% decrease in Cmax and 75% decrease in AUC of eltrombopag. Administration of eltrombopag 2 hours after the high-calcium meal decreased eltrombopag Cmax by 48% and AUC by 47%, while administration 2 hours before the high-calcium meal decreased eltrombopag Cmax by 14% and AUC by 20%.

ADJUST DOSING INTERVAL: Polyvalent cations such as aluminum, calcium, iron, magnesium, and zinc can significantly reduce the gastrointestinal absorption of eltrombopag due to chelation. In one clinical trial, administration of a single 75 mg dose of eltrombopag with an antacid containing 1524 mg aluminum hydroxide and 1425 mg magnesium carbonate resulted in an approximately 70% decrease in eltrombopag Cmax and AUC.

MANAGEMENT: Eltrombopag should be taken on an empty stomach one hour before or two hours after a meal. Additionally, eltrombopag should be taken at least 2 hours before or 4 hours after any products that contain polyvalent cations such as antacids, mineral supplements, dairy products, and fortified juices.