<p><strong>Effect of Other Drugs on Ceritinib</strong>: Strong CYP3A Inhibitors: A strong CYP3A4/P-gp inhibitor (ketoconazole) increased the systemic exposure of Ceritinib so it should be avoided. If concomitant use of strong CYP3A inhibitors including certain antivirals (e.g., ritonavir), macrolide antibiotics (e.g., telithromycin), antifungals (e.g., ketoconazole), and nefazodone is unavoidable, the Ceritinib dose should be reduced by approximately one third, rounded to the nearest multiple of the 150 mg dosage strength. After discontinuation of a strong CYP3A inhibitor, the Ceritinib dose should be resumed that was taken prior to initiating the strong CYP3A inhibitor. Grapefruit and grapefruit juice should not be consumed as they may inhibit CYP3A.<br />
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<strong>Strong CYP3A Inducers</strong>: A strong CYP3A4/P-gp inducer (Rifampin) decreased the systemic exposure of Ceritinib. Concurrent use of strong CYP3A inducers (e.g., Carbamazepine, Phenytoin, Rifampin, and St. John&#39;s Wort) should be avoided during treatment with Ceritinib.<br />
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<strong>Effect of Ceritinib on Other Drugs</strong>: CYP3A Substrates: Ceritinib increased the systemic exposure of a sensitive CYP3A substrate (Midazolam) so it should be avoided. If concomitant use is unavoidable, dose reduction of the sensitive CYP3A substrates should be considered. If Ceritinib is coadministered with other CYP3A substrates, it should be referred to the CYP3A substrate labeling for dosage recommendation with strong CYP3A inhibitors.<br />
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<strong>CYP2C9 Substrates</strong>: Ceritinib increased the systemic exposure of a CYP2C9 substrate (Warfarin). The frequency of INR monitoring should be increased if coadministration with warfarin is unavoidable as the anti-coagulant effect of Warfarin may be enhanced. Coadministration of Ceritinib should be avoided with CYP2C9 substrates for which minimal concentration changes may lead to serious toxicities. If concomitant use of such CYP2C9 substrates is unavoidable, dose reduction should be considered for the coadministered CYP2C9 substrates.</p>