Oral Drug Approved for Certain Lung Cancers
According to gefitinib's labeling, the recommended dosage is one 250-mg tablet taken daily with or without food. Therapy should be briefly interupted if a skin reaction or eye pain occurs or if diarrhea develops and the patient becomes dehydrated or otherwise poorly tolerates the condition. If shortness of breath, cough, or fever develops suddenly or worsens, therapy should be suspended and the pulmonary symptoms promptly investigated. Development of interstitial lung disease, known to occur in about 1 percent of patients and kill one third of those with the complication, warrants discontinuation of gefitinib therapy and appropriate treatment.
Because gefitinib undergoes extensive metabolism by cytochrome P-450 isoenzyme 3A4, the labeling recommends that patients also taking rifampin, phenytoin, or another potent inducer of the enzyme and showing no signs of a severe adverse drug reaction receive 500 mg daily of the anticancer agent. This higher dosage regimen, however, might increase the patient's risk of adverse events, since the clinical studies found a greater toxicity rate among those who received 500 mg/day of the drug instead of 250 mg/day.
Treatment with gefitinib tablets is contraindicated in patients with severe hypersensitivity to the drug, lactose, or any of the other components.
The most common adverse events reported for the 250-mg/day dosage in the studies were diarrhea, rash, acne, dry skin, nausea, and vomiting. Diarrhea affected about half of the patients.
An AstraZeneca spokeswoman said Iressa will first be available around May 23.