Drug Interactions between bortezomib and exenatide

GENERALLY AVOID: Data from in vitro and animal (mice) studies suggest that green tea may antagonize the cytotoxic effects of bortezomib. Polyphenols in green tea such as (-)-epigallocatechin gallate (EGCG) have been shown to block the proteasome inhibitory action of bortezomib in multiple myeloma and glioblastoma cancer cell lines. The mechanism appears to involve a direct chemical reaction between the boronic acid moiety of bortezomib and the 1,2-benzenediol groups present in certain polyphenols leading to inactivation of bortezomib. However, one group of investigators reported that no antagonism of bortezomib was observed in preclinical in vivo experiments where EGCG plasma concentrations are commensurate with dietary or supplemental intake.

MANAGEMENT: Until more data are available, it may be advisable to avoid or limit consumption of green tea and green tea products during treatment with bortezomib. The interaction has not been demonstrated for other, non-boronic acid proteasome inhibitors.

ADJUST DOSING INTERVAL: Exenatide slows gastric emptying and may reduce the extent and rate of absorption of concomitantly administered oral medications. When acetaminophen 1000 mg was administered simultaneously with exenatide 10 mcg and also one hour, 2 hours, and 4 hours after exenatide injection, acetaminophen systemic exposure (AUC) was decreased by 21%, 23%, 24%, and 14%, respectively; peak plasma concentration (Cmax) was decreased by 37%, 56%, 54%, and 41%, respectively; and time to peak plasma concentration (Tmax) was increased from 0.6 hours in the control period to 0.9 hours, 4.2 hours, 3.3 hours, and 1.6 hours, respectively. These values were not significantly changed when acetaminophen was given one hour before exenatide injection.

MANAGEMENT: Concomitantly administered oral medications that are dependent on threshold concentrations for efficacy (e.g., antibiotics, contraceptives) or that require rapid gastrointestinal absorption (e.g., hypnotics, pain medications) should be administered at least 1 hour before exenatide. If such medications are to be administered with food, patients should be advised to take them with a meal or snack when exenatide is not administered.