Drug Interactions between pexidartinib and posaconazole

ADJUST DOSING INTERVAL: The presence of food may increase the absorption and toxicity of pexidartinib. Administration of pexidartinib with a high-fat meal increased peak plasma concentration (Cmax) and systemic exposure (AUC) by 100% and prolonged the time to reach peak plasma concentration (Tmax) by 2.5 hours.

GENERALLY AVOID: Grapefruit or grapefruit juice may increase the plasma concentration and risk of adverse effects of pexidartinib, including potentially fatal hepatotoxicity. The mechanism is inhibition of CYP450 3A4-mediated metabolism of pexidartinib by certain compounds present in grapefruits. Concomitant administration of itraconazole, a strong CYP450 3A4 inhibitor, increased pexidartinib peak plasma concentration (Cmax) and systemic exposure (AUC) by 48% and 70%, respectively.

MANAGEMENT: Pexidartinib should be administered on an empty stomach, at least one hour before or two hours after a meal or snack. Consumption of grapefruit or grapefruit juice should generally be avoided during pexidartinib therapy. If concomitant use is unavoidable, the dose of pexidartinib should be reduced according to the manufacturer's recommendations. If concomitant use of grapefruit or grapefruit juice is discontinued, the dose of pexidartinib may be increased (after 3 plasma half-lives of a strong CYP450 3A4 inhibitor) to the dose that was used prior to consumption of grapefruit or grapefruit juice.

ADJUST DOSING INTERVAL: Food significantly increases the absorption of posaconazole from the oral suspension but only modestly from the delayed-release tablet. Following single-dose administration, posaconazole mean peak plasma concentration (Cmax) and systemic exposure (AUC) are approximately 2.5 to 3 times higher when the oral suspension is given with a nonfat meal or a nutritional supplement (14 grams of fat) than when given under fasting conditions, and approximately 3.5 to 4 times higher when given during or 20 minutes after a high-fat meal (50 grams of fat) than under fasting conditions. Acidic beverages may also increase posaconazole absorption. In 12 healthy volunteers, administration of a single 400 mg dose of posaconazole suspension with 12 ounces of ginger ale increased posaconazole Cmax by 92% and AUC by 70% compared to administration after fasting. In contrast, the Cmax and AUC of posaconazole increased by just 16% and 51%, respectively, when posaconazole tablets were given as a single 300 mg dose to healthy volunteers after a high-fat meal relative to a fasted state.

GENERALLY AVOID Concomitant use of alcohol and posaconazole administered in the form of delayed-release oral suspension may lead to a faster release of posaconazole. An in vitro dissolution study determined a potential for alcohol-induced dose-dumping with the delayed-release oral suspension of posaconazole.

MONITOR: In 5 study subjects, posaconazole Cmax decreased by 27% to 53% and AUC decreased by 33% to 51% when the oral suspension was administered via a nasogastric tube as opposed to orally.

MANAGEMENT: Posaconazole tablets should be taken with food, whereas posaconazole oral suspension should be administered during or immediately (i.e., within 20 minutes) following a full meal to enhance bioavailability. Patients who cannot eat a full meal should take the suspension with a liquid nutritional supplement or an acidic carbonated beverage such as ginger ale. In patients who cannot eat a full meal or tolerate an oral nutritional supplement or an acidic carbonated beverage and who do not have the option of taking another formulation of posaconazole, alternative antifungal therapy should be considered; otherwise, monitor patients closely for breakthrough fungal infections. Patients receiving posaconazole via a nasogastric tube should also be closely monitored due to increased risk of treatment failure associated with lower plasma exposure. Administration of alcohol with posaconazole from the delayed-release oral suspension formulation is not recommended.