Drug Interactions between Orserdu and posaconazole

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of elacestrant, 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 other CYP450 3A4 inhibitors. When elacestrant (172 mg once daily) was administered with itraconazole, a potent CYP450 3A4 inhibitor, elacestrant peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 4.4-fold and 5.3-fold, respectively. Concomitant use of fluconazole, a moderate CYP450 3A4 inhibitor, is predicted to increase elacestrant (345 mg single dose) Cmax and AUC by 1.6-fold and 2.3-fold, respectively. 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 elacestrant may increase the risk of adverse reactions such as musculoskeletal pain, nausea, dyslipidemia, increased liver enzymes, fatigue, decreased hemoglobin, and vomiting.

Administration of elacestrant (345 mg) with a high-fat meal (800 to 1000 calories, 50% fat) increased elacestrant Cmax and AUC by 42% and 22%, respectively, compared to fasted conditions.

MANAGEMENT: It may be advisable for patients to avoid consumption of grapefruit, grapefruit juice, or supplements that contain grapefruit during treatment with elacestrant. Elacestrant should be taken with food at approximately the same time each day.

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.