| Agenta |
Effect |
Mechanism |
|
| CYP3A4 inducers (e.g., phenytoin, carbamazepine, rifampin, barbiturates, St. John’s Wort) |
Decreases gefitinib/erlotinib plasma concentration and reduces efficacy |
Enhances gefitinib/erlotinib CYP3A4 metabolism |
| CYP3A4 inhibitors (e.g., ketoconazole, erythromycin, clarithromycin, protease inhibitors, grapefruit juice) |
Increases gefitinib/erlotinib plasma concentration and increases toxicity |
Decreases gefitinib/erlotinib CYP3A4 metabolism |
| Proton pump inhibitors (e.g., omeprazole) |
Reduces gefitinib absorption (not documented for erlotinib) |
Sustained elevation of gastric pH |
| Histamine H2-receptor antagonists (e.g., ranitidine, cimetidine, famotidine) |
Reduces gefitinib absorption (not documented for erlotinib) |
Sustained elevation of gastric pH |
|
| aTrade names and manufacturers’ information are as follows: phenytoin (Dilantin®; Pfizer Pharmaceuticals, New York, http://www.pfizer.com), carbamazepine (Tegretol®; Novartis Pharmaceuticals Corporation, East Hanover, NJ, http://www.pharma.us.novartis.com), rifampicin (Rifadin®; Aventis Pharmaceuticals Inc., Bridgewater, NJ, http://www.aventispharma-us.com), ketoconazole (Nizoral®; Janssen Pharmaceutica Products), omeprazole (Prilosec®; AstraZeneca Pharmaceuticals, Wilmington, DE, http://www.astrazeneca-us.com), ranitidine (Zantac®; GlaxoSmithKline, Philadelphia, http://www.gsk.com), cimetidine (Tagamet®; GlaxoSmithKline), and famotidine (Pepcid®; Merck & Co., Inc., Whitehouse Station, NJ, http://www.merck.com). |
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