|Iressa||Tablet||250 mg||Oral||Astra Zeneca|
|Iressa||Tablet, film coated||250 mg||Oral||Astra Zeneca Ab|
|Iressa||Tablet, coated||250 mg/1||Oral||Astra Zeneca Lp|
Gefitinib (originally coded ZD1839) is a drug used in the treatment of certain types of cancer. Acting in a similar manner to erlotinib (marketed as Tarceva), gefitinib selectively targets the mutant proteins in malignant cells. It is marketed by AstraZeneca under the trade name Iressa. IRESSA is indicated for the first-line treatment of patients with metastatic non-small cell lung cancer (NSCLC) whose tumors have epidermal growth factor receptor (EGFR) exon 19 deletions or exon 21 (L858R) substitution mutations as detected by an FDA-approved test.
Metastatic Non-Small Cell Lung Cancer
Colorectal Cancers，Head and Neck Carcinoma，Squamous Cell Carcinoma (SCC)，ect；
Absorbed slowly after oral administration with a mean bioavailability of 60%. Peak plasma levels occurs 3-7 hours post-administration. Food does not affect the bioavailability of gefitinib.
Primarily hepatic via CYP3A4. Three sites of biotransformation have been identified: metabolism of the N-propoxymorpholino-group, demethylation of the methoxy-substituent on the quinazoline, and oxidative defluorination of the halogenated phenyl group.
The acute toxicity of gefitinib up to 500 mg in clinical studies has been low. In non-clinical studies, a single dose of 12,000 mg/m2 (about 80 times the recommended clinical dose on a mg/m2 basis) was lethal to rats. Half this dose caused no mortality in mice. Symptoms of overdose include diarrhea and skin rash.