Qualitinib Drug Interactions

In human liver microsome Gefitinib had no inhibitory effect on CYPA2, CYP2C9, and CYP3A4 activities concentrations ranging from 5000 ng/ml. At the highest concentration studied (5000 mg/ml). Gefitinib inhibits CYP2C19 by 24% and CYP2D6 by 43%. Exposure to metoprolol, a substrate of CYP2D6, was increased by 30% where it was given in combination with Gefitinib (500 mg daily for 28 days) in patients with solid tumors.
Rifampicin, an inducer of CYP3A4, reduced mean AUC of Gefitinib by 85% in healthy male volunteers. Concomitant administration of itraconazole (200 mg QD for 12 days), an inhibitor of CYP3A4, with Gefitinib (250 mg single dose) to healthy male volunteers, increased mean Gefitinib AUC by 88%.
Co-administration of high doses of ranitidine with sodium bicarbonate (to maintain the gastric pH above pH 5.0) reduced mean Gefitinib AUC by 44%.
International Normalized Ratio (INR) elevations and/or bleeding events have been reported in some patients taking warfarin while on Gefitinib therapy. Patients taking warfarin should be monitored regularly for changes in prothrombin time or INR.