Drug Interactions between ibrexafungerp and Rifadin IV

GENERALLY AVOID: Concurrent use of rifampin in patients who ingest alcohol daily may result in an increased incidence of hepatotoxicity. The increase in hepatotoxicity may be due to an additive risk as both alcohol and rifampin are individually associated with this adverse reaction. However, the exact mechanism has not been established.

ADJUST DOSING INTERVAL: Administration with food may reduce oral rifampin absorption, increasing the risk of therapeutic failure or resistance. In a randomized, four-period crossover phase I study of 14 healthy male and female volunteers, the pharmacokinetics of single dose rifampin 600 mg were evaluated under fasting conditions and with a high-fat meal. Researchers observed that administration of rifampin with a high-fat meal reduced rifampin peak plasma concentration (Cmax) by 36%, nearly doubled the time to reach peak plasma concentration (Tmax) but reduced overall exposure (AUC) by only 6%.

MANAGEMENT: The manufacturer of oral forms of rifampin recommends administration on an empty stomach, 30 minutes before or 2 hours after meals. Patients should be encouraged to avoid alcohol or strictly limit their intake. Patients who use alcohol and rifampin concurrently or have a history of alcohol use disorder may require additional monitoring of their liver function during treatment with rifampin.

GENERALLY AVOID: Coadministration with grapefruit juice may increase the plasma concentrations of ibrexafungerp. The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. 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. Pharmacokinetic interactions involving grapefruit juice are also subject to a high degree of interpatient variability, thus the extent to which a given patient may be affected is difficult to predict. In healthy subjects receiving the potent CYP450 3A4 inhibitor ketoconazole (400 mg once daily for 15 days), ibrexafungerp peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 2.5-fold and 5.8-fold, respectively. Increased plasma concentrations of ibrexafungerp may increase the risk for adverse effects such as diarrhea, nausea, abdominal pain, dizziness, and vomiting.

When administered to healthy volunteers with a high-fat meal (800 to 1000 calories; 50% fat), ibrexafungerp Cmax and AUC increased 32% and 38%, respectively, compared to fasted conditions.

MANAGEMENT: Ibrexafungerp may be administered with or without food. However, avoiding consumption of grapefruit or grapefruit juice during treatment with ibrexafungerp may be advisable.