Introduction
Gefitinib is an oral medication used primarily in the treatment of non-small cell lung cancer (NSCLC). It is a tyrosine kinase inhibitor that targets and blocks the epidermal growth factor receptor (EGFR), which plays a critical role in the growth and spread of cancer cells.
Uses
Gefitinib is used for:
- Treating advanced or metastatic non-small cell lung cancer (NSCLC) in patients with specific mutations in the EGFR gene.
- Managing NSCLC after prior chemotherapy or other treatments have failed.
- Used as first-line therapy for patients with EGFR-mutant NSCLC.
| Brand Name | Gefitinib |
|---|---|
| Type | |
| Weight | |
| Generic | Gefitinib |
| Manufacturer | |
| Available in | English বাংলা |
Mechanism of Action
Gefitinib works by selectively inhibiting the tyrosine kinase activity of the EGFR. EGFR is a receptor on the surface of cells that, when activated, promotes cell proliferation and survival. By blocking this receptor, Gefitinib impedes the signaling pathways involved in cancer cell growth and division.
How Long Does It Take to Work?
Patients may start to see clinical benefits from Gefitinib within a few weeks of initiating treatment. However, the full therapeutic effect might take several months to become evident. Regular monitoring by a healthcare provider is necessary to assess response and adjust treatment as needed.
Absorption
Gefitinib is well-absorbed from the gastrointestinal tract. It has an oral bioavailability of about 60%, meaning that a substantial portion of the drug is absorbed into the bloodstream when taken orally. Food can affect the absorption rate, but it is generally recommended to take the medication on an empty stomach to maximize absorption.
Route of Elimination
Gefitinib is primarily eliminated through the liver. It is metabolized extensively by the liver and excreted in the bile. Only a small fraction of the drug is excreted unchanged in the urine.
Dosage
Recommended dose: 250 mg Gefitinib orally once daily with or without food until disease progression or unacceptable toxicity. One should not take a missed dose within 12 hours of the next dose.Administration to Patients who have Difficulty Swallowing Solids: Gefitinib tablets should be immersed in 4 to 8 ounces of water by dropping the tablet in water, and stirred for approximately 15 minutes. The liquid should be immediately drunk or administered through a naso-gastric tube. The container should be rinsed with 4 to 8 ounces of water and immediately drunk or administered through the naso- gastric tube.
The typical dosage of Gefitinib is 250 mg orally once daily. The exact dosage may be adjusted based on the patient’s response and tolerance to the medication. Dosage adjustments may also be necessary in cases of liver impairment or in combination with other medications.
Administration
Gefitinib is administered orally in the form of tablets. It should be taken with a full glass of water. It is usually taken once daily, and it is important to follow the prescribed dosage schedule to maintain effective drug levels and reduce the risk of side effects.
Side Effects
Common side effects of Gefitinib include:
- Diarrhea
- Skin rash
- Acne
- Nausea
- Fatigue
Serious side effects can include interstitial lung disease (ILD), liver enzyme abnormalities, and severe skin reactions. Patients should report any unusual symptoms to their healthcare provider promptly.
Toxicity
Toxicity related to Gefitinib can manifest as severe skin reactions, liver damage, or ILD. Monitoring liver function tests and respiratory symptoms is crucial during treatment. In cases of severe toxicity, dose adjustment or discontinuation of the drug may be necessary.
Precautions
Precautions when using Gefitinib include:
- Regular monitoring of liver function and respiratory status.
- Close observation for signs of skin reactions or rash.
- Not recommended for use in patients with severe liver impairment without careful consideration and monitoring.
Interaction
Gefitinib can interact with other medications, including:
- CYP3A4 inhibitors (e.g., ketoconazole) which can increase Gefitinib levels in the blood.
- CYP3A4 inducers (e.g., rifampin) which can decrease Gefitinib levels and reduce its effectiveness.
Patients should inform their healthcare provider of all medications they are taking to manage potential interactions.
Disease Interaction
Gefitinib should be used with caution in patients with a history of interstitial lung disease or severe hepatic impairment. It may also need to be adjusted for patients with other conditions that affect liver function or those undergoing concurrent treatments that impact liver metabolism.
Drug Interaction
Gefitinib 's interactions with other drugs can influence its efficacy and safety. For example, drugs that affect CYP3A4 enzyme activity can alter Gefitinib 's plasma concentration. It is important to manage these interactions carefully to maintain the effectiveness and minimize side effects.
Food Interactions
Food can affect the absorption of Gefitinib . It is generally advised to take Gefitinib on an empty stomach to enhance absorption. Consuming food, especially high-fat meals, may decrease the absorption of the medication and affect its efficacy.
Pregnancy Use
Gefitinib is not recommended for use during pregnancy due to potential risks to the fetus. It is classified as a Category D drug, meaning there is evidence of potential harm to the fetus based on human studies. Women of childbearing age should use effective contraception while on Gefitinib .
Lactation Use
Gefitinib is not recommended for use during breastfeeding. It is not known whether Gefitinib is excreted in human breast milk, but due to potential risks to the infant, breastfeeding is generally advised against while on this medication.
Acute Overdose
In the case of an acute overdose of Gefitinib , symptoms might include severe gastrointestinal effects or liver toxicity. Immediate medical attention is necessary. Treatment may involve supportive care and symptomatic management.
Contraindication
Gefitinib is contraindicated in patients with known hypersensitivity to the drug or any of its components. It should be used with caution in patients with severe hepatic impairment or a history of severe lung disease.
Use Direction
Follow the healthcare provider's instructions for dosing and administration. Take Gefitinib exactly as prescribed, usually 250 mg orally once daily, and do not alter the dosage without consulting a healthcare provider.
Storage Conditions
Store Gefitinib at room temperature, away from moisture and direct light. Keep it in its original container to protect from moisture. Ensure it is kept out of reach of children and disposed of properly if expired or no longer needed.
Volume of Distribution
The volume of distribution for Gefitinib is approximately 1.5 L/kg, reflecting its distribution within the body tissues. This value helps in understanding how the drug disperses throughout the body after administration.
Half Life
The half-life of Gefitinib is approximately 48 hours, indicating the time it takes for the plasma concentration of the drug to reduce by half. This allows for once-daily dosing in most cases.
Clearance
Gefitinib is primarily cleared through the liver. The clearance rate can be influenced by liver function and other factors, including interactions with medications that affect liver enzyme activity.
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