Drug Interaction Report

GENERALLY AVOID: Coadministration with potent inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of trabectedin, which is primarily metabolized by the isoenzyme. In eight study patients with advanced malignancies, administration of a single 0.58 mg/m2 infusion of trabectedin following the second dose of ketoconazole (200 mg twice daily for 15 doses), a potent CYP450 3A4 inhibitor, increased the dose-normalized mean trabectedin peak plasma concentration (Cmax) and systemic exposure (AUC) by 22% and 66%, respectively, compared to infusion of a single 1.3 mg/m2 dose of trabectedin alone.

MANAGEMENT: Concomitant use of trabectedin with potent CYP450 3A4 inhibitors should generally be avoided. Some authorities recommend avoiding concomitant use of trabectedin during and for 2 weeks after treatment with itraconazole. If a potent CYP450 3A4 inhibitor is required for short-term use (i.e., less than 14 days), it is advisable to administer the CYP450 3A4 inhibitor one week after the trabectedin infusion and discontinue it the day prior to the next infusion. Close monitoring for toxicities such as myelosuppression, rhabdomyolysis, hepatotoxicity, and cardiomyopathy is recommended during long-term coadministration, and the trabectedin dosage adjusted accordingly or treatment discontinued as necessary.

ADJUST DOSING INTERVAL: Food reduces the oral absorption and bioavailability of voriconazole. According to the product labeling, administration of multiple doses of voriconazole with high-fat meals decreased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) by 34% and 24%, respectively, when the drug is administered as a tablet, and by 58% and 37%, respectively, when administered as the oral suspension.

MANAGEMENT: To ensure maximal oral absorption, voriconazole tablets and oral suspension should be taken at least one hour before or after a meal.

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

GENERALLY AVOID: Coadministration of trabectedin with other agents known to induce hepatotoxicity such as alcohol may potentiate the risk of liver injury. Reversible, acute increases in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) have occurred frequently in patients treated with trabectedin alone or with pegylated liposomal doxorubicin in clinical trials. In one U.S. trial with 378 patients, grade 3 or 4 elevated liver function tests (defined as elevations in ALT, AST, total bilirubin, or alkaline phosphatase) were reported in 35% of patients receiving trabectedin. ALT or AST elevations greater than eight times the upper limit of normal (ULN) occurred in 18% of patients, and drug-induced liver injury (defined as concurrent elevations in ALT or AST more than three times ULN, alkaline phosphatase less than two times ULN, and total bilirubin at least two times ULN) occurred in 1.3% of patients.

MANAGEMENT: Consumption of grapefruit or grapefruit juice during treatment with trabectedin should be avoided. Excessive use of alcohol is also not recommended. Patients should be advised to seek medical attention if they experience potential signs and symptoms of hepatotoxicity such as fever, rash, itching, anorexia, nausea, vomiting, fatigue, malaise, right upper quadrant pain, dark urine, pale stools, and jaundice. Monitoring of alkaline phosphatase, bilirubin, AST, and ALT should occur regularly during trabectedin treatment in accordance with the product labeling, or as often as necessary when clinical symptoms develop. Trabectedin must not be used in patients with elevated bilirubin at the time of initiation of cycle. Elevated liver function tests should be managed with treatment interruption, dosage reduction, or permanent discontinuation depending on the severity and duration of abnormality.