Erlotinibinteractions

CYP3A4 Inhibitors Co-administration of erlotinib with a strong CYP3A4 inhibitor or a combined CYP3A4 and CYP1A2 inhibitor increased erlotinib exposure. Erlotinib is metabolized primarily by CYP3A4 and to a lesser extent by CYP1A2. Increased erlotinib exposure may increase the risk of exposure-related toxicity. Avoid co-administering erlotinib with strong CYP3A4 inhibitors (e.g., boceprevir, clarithromycin, conivaptan, indinavir, itraconazole, ketoconazole, lopinavir/ritonavir, nefazodone, nelfinavir, posaconazole, ritonavir, saquinavir, telithromycin, voriconazole, grapefruit or grapefruit juice) or a combined CYP3A4 and CYP1A2 inhibitor (e.g., ciprofloxacin). Reduce the erlotinib dosage when co-administering with a strong CYP3A4 inhibitor or a combined CYP3A4 and CYP1A2 inhibitor if co-administration is unavoidable. CYP3A4 Inducers Pre-treatment with a CYP3A4 inducer prior to erlotinib decreased erlotinib exposure. Increase the erlotinib dosage if co-administration with CYP3A4 inducers (e.g., carbamazepine, phenytoin, rifampin, rifabutin, rifapentine, phenobarbital and St. John's wort) is unavoidable. CYP1A2 Inducers and Cigarette Smoking Cigarette smoking decreased erlotinib exposure. Avoid smoking tobacco (CYP1A2 inducer) and avoid concomitant use of erlotinib with moderate CYP1A2 inducers (e.g., teriflunomide, rifampin, or phenytoin). Increase the erlotinib dosage in patients that smoke tobacco or when co-administration with moderate CYP1A2 inducers is unavoidable. Drugs the Increase Gastric pH Co-administration of erlotinib with proton pump inhibitors (e.g., omeprazole) and H-2 receptor antagonists (e.g., ranitidine) decreased erlotinib exposure. For proton pump inhibitors, avoid concomitant use if possible. For H-2 receptor antagonists and antacids, modify the dosing schedule. Increasing the dose of erlotinib when co-administered with gastric PH elevating agents is not likely to compensate for the loss of exposure. Anticoagulants Interaction with coumarin-derived anticoagulants, including warfarin, leading to increased International Normalized Ratio (INR) and bleeding adverse reactions, which in some cases were fatal, have been reported in patients receiving erlotinib. Regularly monitor prothrombin time or INR in patients taking coumarin-derived anticoagulants. Dose modifications of erlotinib are not recommended. CYP3A4 inhibitors or a combined CYP3A4 and CYP1A2 inhibitor increase erlotinib plasma concentrations. Avoid concomitant use. If not possible, reduce erlotinib dose. CYP3A4 inducers decrease erlotinib plasma concentrations. Avoid concomitant use. If not possible, increase erlotinib dose. Cigarette smoking and CYP1A2 inducers decrease erlotinib plasma concentrations. Avoid concomitant use. If not possible, increase erlotinib dose. Drugs that increase gastric pH decrease erlotinib plasma concentrations. For proton pump inhibitors avoid concomitant use if possible. For H-2 receptor antagonists, take erlotinib 10 hours after H-2 receptor antagonist dosing. For use with antacids, separate dosing by several hours.