GENERIC NAME: Gefitinib
BRAND NAME: Iressa
DRUG CLASS AND MECHANISM: Gefitinib is a drug that is used to treat several types of lung cancer. It works by preventing lung cancer cells from growing and multiplying.
Many cells, including cancer cells, have receptors on their surfaces for epidermal growth factor (EGF), a protein that is normally produced by the body and that promotes the growth and multiplication of cells. When EGF attaches to epidermal growth factor receptors (EGFRs), it causes an enzyme called tyrosine kinase to become active within the cells. Tyrosine kinase triggers chemical processes that cause the cells, including cancer cells, to grow, multiply, and spread. Gefitinib attaches to EGFRs and thereby blocks the attachment of EGF and the activation of tyrosine kinase. This mechanism for stopping cancer cells from growing and multiplying is very different from the mechanisms of chemotherapy and hormonal therapy. Gefitinib was approved by the FDA in May of 2003.
PRESCRIBED FOR: Gefitinib is used alone (monotherapy) for the treatment of patients with a certain type of lung cancer (non-small cell lung cancer or NSCLC) that has not responded to chemotherapy.
Lung cancer is the second most common cancer in both men and women and is the leading cause of deaths from cancer in the US. Lung cancer is divided into two major types: small cell lung cancer and NSCLC. NSCLC is the most common type, accounting for almost 80% of lung cancers. There are five subtypes of NSCLC, each of which is made up of different kinds of cancer cells. The cancer cells of each type differ in size, shape, and chemical make-up, and grow and spread in different ways. The three most common types of NSCLC are squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. About one in ten people with NSCLC who receive gefitinib will have a substantial reduction in the size of their cancers, even after other drugs have failed; however, the cancer is not cured.
DOSING: Gefitinib is taken by mouth. The dose is 250 mg once daily. The dose is the same for men or women of any age or weight, and gefitinib can be taken with or without food
USES: This medication is used alone to treat lung cancer after other cancer chemotherapy treatments have not been successful. It is a cancer chemotherapy drug which works by blocking a certain protein (an enzyme called tyrosine kinase) which may help cancer grow and spread.
HOW TO USE: Take gefitinib by mouth once daily, with or without food, or as directed. Medications which reduce or completely block stomach acid (e.g., proton pump inhibitors/PPIs, H2 blockers, antacids) may decrease the absorption of gefitinib. This could decrease the effectiveness of gefitinib. Consult your doctor or pharmacist if you are taking any of these medications. Use this medication regularly in order to get the most benefit from it. To help you remember, use it at the same time each day.
DRUG INTERACTIONS: Gefitinib may increase the blood-thinning effects of warfarin (Coumadin) and increase the risk of bleeding. Therefore, patients receiving gefitinib and warfarin at the same time should have more frequent testing of the “thinness” of their blood. Patients who receive drugs that increase an enzyme in the liver called CYP 3A4 that destroys gefitinib (e.g., rifampin or phenytoin (Dilantin) may need a higher dose of gefitinib to maintain the effectiveness of gefitinib. Similarly, patients who receive drugs that reduce CYP 3A4, e.g., ketoconazole (Nizoral), itraconazole (Sporanox), fluconazole (Diflucan), erythromycin, clarithromycin (Biaxin), ritonavir (Norvir), nelfinavir (Viracept), indinavir (Crixivan), nefazodone (Serzone), as well as grapefruit juice, may need a lower dose of gefitinib to prevent side effects from increased levels of gefitinib.
PREGNANCY: Gefitinib should not be used by pregnant women.
NURSING MOTHERS: It is not known whether gefitinib is secreted in human milk. Since there is a possibility of toxicity in nursing infants, it is recommended that breast feeding be stopped if the mother is treated with gefitinib.
SIDE EFFECTS: About one in one hundred persons receiving gefitinib develop a potentially serious lung condition called interstitial lung disease that causes inflammation within the lung. Therefore, patients taking gefitinib who develop new or worsening cough, fever, or difficulty in breathing should contact their physician immediately. Eye irritation has been observed in patients receiving gefitinib, and patients who develop the onset of new eye symptoms should contact their physician. All patients taking gefitinib should seek medical advice promptly if they develop severe or persistent diarrhea, nausea, loss of appetite, or vomiting.