Drug Interactions between capivasertib and erythromycin

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of capivasertib, 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 studied with other CYP450 3A4 inhibitors. Based on clinical studies and model-informed approaches, concomitant use with the potent CYP450 3A4 inhibitor itraconazole is predicted to increase capivasertib systemic exposure (AUC) by up to 1.7-fold and peak plasma concentration (Cmax) by up to 1.4-fold. Coadministration with the moderate CYP450 3A4 inhibitors erythromycin and verapamil is predicted to increase the AUC and Cmax of capivasertib by up to 1.5-fold 1.3-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 capivasertib may increase the risk of adverse effects such as diarrhea, cutaneous adverse reactions, decreased lymphocytes, decreased hemoglobin, hyperglycemia, nausea, and fatigue.

MANAGEMENT: It may be advisable for patients to avoid the consumption of grapefruit, grapefruit juice, or supplements that contain grapefruit during treatment with capivasertib.

ADJUST DOSING INTERVAL: Food may variably affect the bioavailability of different oral formulations and salt forms of erythromycin. The individual product package labeling should be consulted regarding the appropriate time of administration in relation to food ingestion. Grapefruit juice may increase the plasma concentrations of orally administered erythromycin. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. In an open-label, crossover study consisting of six healthy subjects, the coadministration with double-strength grapefruit juice increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of a single dose of erythromycin (400 mg) by 52% and 49%, respectively, compared to water. The half-life was not affected. The clinical significance of this potential interaction is unknown.

MANAGEMENT: In general, optimal serum levels are achieved when erythromycin is taken in the fasting state, one-half to two hours before meals. However, some erythromycin products may be taken without regard to meals.

Ethanol, when combined with erythromycin, may delay absorption and therefore the clinical effects of the antibiotic. The mechanism appears to be due to slowed gastric emptying by ethanol. Data is available only for erythromycin ethylsuccinate. Patients should be advised to avoid ethanol while taking erythromycin salts.