Drug Interaction Report

GENERALLY AVOID: Coadministration with inhibitors of the hepatic uptake transporters organic anion transporting polypeptides (OATP) 1B1 and/or OATP 1B3 may increase the plasma concentrations of resmetirom, which has been shown to be a substrate and inhibitor of these transporters in vitro. This may increase the risk and/or severity of resmetirom-related adverse effects (e.g., hepatotoxicity, gallbladder-related adverse reactions, diarrhea, nausea, pruritus, vomiting, constipation, abdominal pain, dizziness); however, clinical data are not available.

MANAGEMENT: According to the manufacturer of resmetirom, concomitant use with inhibitors of OATP 1B1 and/or OATP 1B3 should generally be avoided.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of lapatinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits.

ADJUST DOSING INTERVAL: Food can significantly increase the oral bioavailability of lapatinib. According to the manufacturer, lapatinib peak plasma concentration (Cmax) was approximately 2.5- and 3-fold higher and systemic exposure (AUC) 3- and 4-fold higher when administered with a low fat meal (5% fat; 500 calories) or with a high-fat meal (50% fat; 1000 calories), respectively, compared to fasting. Dividing the daily dose also resulted in an approximately 2-fold higher systemic exposure at steady state compared to the same total dose administered once daily.

MANAGEMENT: Patients treated with lapatinib should preferably avoid the consumption of grapefruit or grapefruit juice. The manufacturer recommends that lapatinib be administered at least one hour before or one hour after a meal. The lapatinib dose is administered once daily and should not be divided.