Drug Interaction Report

Coadministration with potent inducers of CYP450 3A4 may decrease exposure to unconjugated monomethyl auristatin E (MMAE), the anti-mitotic and cytotoxic component of polatuzumab vedotin. Polatuzumab vedotin is an antibody-drug conjugate (ADC) that releases MMAE via proteolytic cleavage, and MMAE has been shown in vitro to be primarily metabolized by CYP450 3A4. Concomitant use of polatuzumab vedotin with rifampin, a potent CYP450 3A4 inducer, is predicted to decrease unconjugated MMAE exposure (AUC) by 63% according to the product labeling. However, the clinical relevance is unknown, since the intact ADC containing the antibody component is required to bind to CD79b, the specific surface protein found on B cell receptors, which allows for internalization and cleavage by lysosomal proteases to enable intracellular delivery of MMAE.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of carbamazepine. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

In a small, randomized, crossover study, the administration of carbamazepine with grapefruit juice (compared to water) increased plasma drug concentrations by approximately 40%. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits.

MANAGEMENT: Patients receiving carbamazepine should be advised to avoid or limit consumption of alcohol. Given the drug's narrow therapeutic index, patients receiving carbamazepine therapy should preferably avoid the regular consumption of grapefruits and grapefruit juice to prevent any undue fluctuations in plasma drug levels. Patients should be advised to report signs of carbamazepine toxicity (nausea, visual disturbances, dizziness, or ataxia) to their physicians.