Drug Interactions between entrectinib and lorlatinib

GENERALLY AVOID: Grapefruit and grapefruit juice may significantly increase the plasma concentrations of lorlatinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruit. Because grapefruit juice inhibits primarily intestinal rather than hepatic CYP450 3A4, the magnitude of interaction is greatest for those drugs that undergo significant presystemic metabolism by CYP450 3A4 (i.e., drugs with low oral bioavailability). 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. Pharmacokinetic interactions involving grapefruit juice are also subject to a high degree of interpatient variability, thus the extent to which a given patient may be affected is difficult to predict.

MANAGEMENT: Patients treated with lorlatinib should avoid consumption of grapefruit, grapefruit juice, and any supplement containing grapefruit extract. If coadministration is unavoidable, some authorities recommend reducing the initial dosage of lorlatinib from 100 mg orally once daily to 75 mg orally once daily. In patients who have had a dosage reduction to 75 mg orally once daily due to adverse reactions, the lorlatinib dosage should be further reduced to 50 mg orally once daily upon initiation of a potent CYP450 3A4 inhibitor. After 3 plasma half-lives following discontinuation of the potent CYP450 3A4 inhibitor, the lorlatinib dosage may be increased to that used prior to initiation of the inhibitor.

GENERALLY AVOID: Grapefruit juice and Seville oranges may increase the plasma concentrations of entrectinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit and Seville oranges Inhibition of hepatic CYP450 3A4 may also contribute. The interaction has not been studied with grapefruit juice, but pharmacokinetic data are available for the potent CYP450 3A4 inhibitor, itraconazole. When a single 100 mg dose of entrectinib was administered with itraconazole, entrectinib peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 1.7- and 6-fold, respectively. Coadministration of entrectinib with a moderate CYP450 3A4 inhibitor is predicted to increase entrectinib Cmax and AUC by 2.9- and 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 entrectinib may increase the risk and/or severity of adverse effects such as cognitive impairment, mood disorders, dizziness, sleep disturbances, liver enzyme elevations, hyperuricemia, congestive heart failure, edema, myocarditis, QT prolongation, vision problems, anemia, and neutropenia.

MANAGEMENT: Patients should avoid consumption of grapefruit, grapefruit juice, and Seville oranges during treatment with entrectinib.

The recommended maximum number of medicines in the 'multikinase inhibitors' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'multikinase inhibitors' category:

• entrectinib
• lorlatinib

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.