Topic: Warning! Omeprazole Highly Affects the Absorption of Tarceva
The following information can be found at http://www.rxlist.com/tarceva-durg.htm (After reading the last paragraph on page three, click on the "clinical pharmacology" link:
Absorption and Distribution:
Erlotinib is about 60% absorbed after oral administration and its bioavailability is substantially increased by food to almost 100%. Peak plasma levels occur 4 hours after dosing. The solubility of erlotinib is pH dependent. Erlotinib solubility decreases as pH increases. Co-administration of TARCEVA with omeprazole, a proton pump inhibitor, decreased the erlotinib exposure [AUC] and maximum concentration [Cmax] by 46% and 61% respectively. When TARCEVA was administered 2 hours following a 300 mg dose of ranitidine, an H2 receptor antagonist, the erlotinib AUC was reduced by 33% and Cmax by 54%. When TARCEVA was administered with ranitidine 150 mg twice daily (at least 10 h after the previous ranitidine evening dose and 2 h before the ranitidine morning dose), the erlotinib AUC and Cmax decreased by 15% and 17% respectively [see DRUG INTERACTIONS].