Drug Interactions between Acid Controller Complete Dual Action and gefitinib

ADJUST DOSING INTERVAL: Coadministration with drugs that elevate gastric pH such as H2-receptor antagonists and antacids may decrease the plasma concentrations of gefitinib. According to the manufacturer, the solubility of gefitinib is pH-dependent and decreases sharply between pH 4 and 6, becoming practically insoluble above pH 7. When gefitinib 250 mg was administered to healthy male volunteers (n=26) one hour following two oral 450 mg doses of ranitidine with sodium bicarbonate as needed to achieve a sustained gastric pH above 5.0, mean gefitinib peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by 71% and 47%, respectively, compared to administration of gefitinib alone. High doses of short-acting antacids may have a similar effect if taken regularly in close proximity to gefitinib administration.

MANAGEMENT: The possibility of a diminished therapeutic response to gefitinib should be considered during coadministration with H2-receptor antagonists or antacids. If concomitant treatment is required, the manufacturer recommends administering gefitinib 6 hours before or 6 hours after an H2-receptor antagonist or antacid.

ADJUST DOSING INTERVAL: Coadministration with drugs that elevate gastric pH such as H2-receptor antagonists and antacids may decrease the plasma concentrations of gefitinib. According to the manufacturer, the solubility of gefitinib is pH-dependent and decreases sharply between pH 4 and 6, becoming practically insoluble above pH 7. When gefitinib 250 mg was administered to healthy male volunteers (n=26) one hour following two oral 450 mg doses of ranitidine with sodium bicarbonate as needed to achieve a sustained gastric pH above 5.0, mean gefitinib peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by 71% and 47%, respectively, compared to administration of gefitinib alone. High doses of short-acting antacids may have a similar effect if taken regularly in close proximity to gefitinib administration.

MANAGEMENT: The possibility of a diminished therapeutic response to gefitinib should be considered during coadministration with H2-receptor antagonists or antacids. If concomitant treatment is required, the manufacturer recommends administering gefitinib 6 hours before or 6 hours after an H2-receptor antagonist or antacid.

ADJUST DOSING INTERVAL: Coadministration with drugs that elevate gastric pH such as H2-receptor antagonists and antacids may decrease the plasma concentrations of gefitinib. According to the manufacturer, the solubility of gefitinib is pH-dependent and decreases sharply between pH 4 and 6, becoming practically insoluble above pH 7. When gefitinib 250 mg was administered to healthy male volunteers (n=26) one hour following two oral 450 mg doses of ranitidine with sodium bicarbonate as needed to achieve a sustained gastric pH above 5.0, mean gefitinib peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by 71% and 47%, respectively, compared to administration of gefitinib alone. High doses of short-acting antacids may have a similar effect if taken regularly in close proximity to gefitinib administration.

MANAGEMENT: The possibility of a diminished therapeutic response to gefitinib should be considered during coadministration with H2-receptor antagonists or antacids. If concomitant treatment is required, the manufacturer recommends administering gefitinib 6 hours before or 6 hours after an H2-receptor antagonist or antacid.

Antacids and some aluminum, calcium, and magnesium salts may decrease the plasma concentrations of H2-receptor antagonists during oral coadministration. The mechanism of interaction is unknown, but may involve reduced oral absorption due to increased gastric pH. Study data vary, with no changes to nearly 60% reductions in systemic exposures (AUCs) reported for cimetidine, famotidine, and ranitidine. The clinical significance has not been established. As a precaution, patients may consider taking H2-receptor antagonists one to two hours before antacids.

Antacids and some aluminum, calcium, and magnesium salts may decrease the plasma concentrations of H2-receptor antagonists during oral coadministration. The mechanism of interaction is unknown, but may involve reduced oral absorption due to increased gastric pH. Study data vary, with no changes to nearly 60% reductions in systemic exposures (AUCs) reported for cimetidine, famotidine, and ranitidine. The clinical significance has not been established. As a precaution, patients may consider taking H2-receptor antagonists one to two hours before antacids.