Drug Interaction Report

GENERALLY AVOID: Theoretically, proton pump inhibitors may decrease the gastrointestinal absorption of enteric-coated naproxen, which requires an acidic environment for dissolution. The proposed mechanism is an increase in gastric pH (i.e. decreased gastric acidity) induced by proton pump inhibitors. In patients treated with proton pump inhibitors, the possibility of a reduced or subtherapeutic response to enteric-coated naproxen should be considered.

MANAGEMENT: Concomitant use of these drugs is generally not recommended.

Since the aqueous solubility of axitinib is pH-dependent, with higher pH resulting in lower solubility, drugs that increase the pH of the upper gastrointestinal tract may reduce the oral bioavailability of axitinib. The interaction has been studied with rabeprazole. When given with rabeprazole (20 mg once daily for 5 days), axitinib peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by approximately 50% and 20%, respectively. These changes are not considered clinically significant. No dosage adjustment for axitinib is recommended during coadministration with proton pump inhibitors, H2-receptor antagonists, or antacids.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of axitinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit.

MANAGEMENT: Patients treated with axitinib should avoid consumption of grapefruit, grapefruit juice, and any supplement containing grapefruit extract. Axitinib may be administered with or without food.

GENERALLY AVOID: The concurrent use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) and ethanol may lead to gastrointestinal (GI) blood loss. The mechanism may be due to a combined local effect as well as inhibition of prostaglandins leading to decreased integrity of the GI lining.

MANAGEMENT: Patients should be counseled on this potential interaction and advised to refrain from alcohol consumption while taking aspirin or NSAIDs.

MONITOR: Smoking cessation may lead to elevated plasma concentrations and enhanced pharmacologic effects of drugs that are substrates of CYP450 1A2 (and possibly CYP450 1A1) and/or certain drugs with a narrow therapeutic index (e.g., flecainide, pentazocine). One proposed mechanism is related to the loss of CYP450 1A2 and 1A1 induction by polycyclic aromatic hydrocarbons in tobacco smoke; when smoking cessation agents are initiated and smoking stops, the metabolism of certain drugs may decrease leading to increased plasma concentrations. The mechanism by which smoking cessation affects narrow therapeutic index drugs that are not known substrates of CYP450 1A2 or 1A1 is unknown. The clinical significance of this interaction is unknown as clinical data are lacking.

MANAGEMENT: Until more information is available, caution is advisable if smoking cessation agents are used concomitantly with drugs that are substrates of CYP450 1A2 or 1A1 and/or those with a narrow therapeutic range. Patients receiving smoking cessation agents may require periodic dose adjustments and closer clinical and laboratory monitoring of medications that are substrates of CYP450 1A2 or 1A1.