Other Names/Brands

Imafer, Glivec, Tinibat, Nivec, Itib, Imatero, Imasonib, Mianib, Imnib, Leukivec, Imanib, Imatin

Mechanism of Action

Imatinib is a drug that works as a tyrosine kinase inhibitor, an enzyme that plays a key role in cell growth and division. This drug specifically targets the BCR-ABL protein, the result of a genetic abnormality (chromosomal translocation) found in chronic myeloid leukemia (CML) and several other types of cancer.

By inhibiting the activity of the BCR-ABL enzyme, imatinib prevents the signals that trigger cancer cell growth, thereby inhibiting malignant cell growth and promoting abnormal cell death. This selective mechanism of action makes imatinib effective in suppressing cancer development without significantly harming normal body cells.

Indications

Imatinib is indicated for the treatment of various types of cancer caused by abnormal activation of tyrosine kinases. The primary indication for imatinib is Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia (CML).

Imatinib is also used for Ph+ acute lymphoblastic leukemia (ALL), gastrointestinal stromal tumors (GIST) positive for KIT (CD117) mutations, dermatofibrosarcoma protuberans (DFSP), and several other myeloproliferative disorders associated with mutations in the PDGFR or FIP1L1-PDGFRα genes. The use of imatinib is tailored to the results of molecular testing to determine the specific target that the drug can inhibit.

Contraindications

Imatinib is contraindicated in patients with hypersensitivity to imatinib or any of its components. Pregnant women should also avoid use of this drug unless the expected benefits outweigh the potential risks, as imatinib may cause teratogenic effects on the fetus.

Particular caution is required in patients with severe liver, kidney, or heart dysfunction, as drug metabolism and elimination may be impaired, increasing the likelihood of toxic effects. Before initiating therapy, the patient's medical condition should be evaluated to ensure there are no factors that could exacerbate the drug's side effects.

Side Effects

Side effects of imatinib are generally mild to moderate and can include nausea, vomiting, diarrhea, abdominal pain, muscle cramps, fatigue, and edema (swelling), especially around the eyes and ankles. Some patients may also experience skin rashes, headaches, or decreased appetite.

More severe, but rare, side effects include bone marrow suppression (such as anemia, neutropenia, and thrombocytopenia), liver dysfunction, and heart or kidney problems. Regular monitoring of blood, liver, and kidney function is recommended during imatinib use to detect side effects early.

Preparations

Imatinib is available as a film-coated tablet for oral administration. These tablets generally contain imatinib mesylate in a dosage strength of 100 mg or 400 mg, adjusted based on the patient's condition and response to therapy. The tablet formulation is designed to ensure optimal gastrointestinal absorption and facilitate long-term administration. Imatinib should be taken with food to reduce the risk of stomach irritation.

Dosage

The dosage of imatinib varies depending on the type of disease, its severity, and the patient's response to treatment. In chronic myeloid leukemia (CML), the usual starting dose is 400 mg once daily, while in gastrointestinal stromal tumors (GIST), the starting dose is usually 400–600 mg per day. The dose can be increased to 800 mg per day in cases that do not respond well to initial therapy.

Safety of Drugs

Imatinib is classified as pregnancy category D by the FDA, meaning there is positive evidence of human fetal risk. However, the drug may be used if the potential benefits outweigh the potential risks, such as in life-threatening conditions.

Animal studies and human reports indicate that imatinib can cause fetal abnormalities (teratogenicity) and reproductive toxicity. Therefore, imatinib should be used with extreme caution in pregnant women, and women of childbearing age are advised to use effective contraception during therapy.

Drug Interactions

Imatinib can interact with various other drugs because it is metabolized primarily by the CYP3A4 enzyme in the liver. Drugs that induce CYP3A4, such as rifampin, phenytoin, or carbamazepine, can decrease imatinib blood levels, thereby reducing its effectiveness.

Drugs that inhibit CYP3A4, such as ketoconazole, erythromycin, or clarithromycin, can increase imatinib levels, potentially causing toxicity. Furthermore, imatinib can also affect the levels of other drugs, such as warfarin or simvastatin. Therefore, close monitoring and dose adjustments may be necessary when imatinib is used concomitantly with other medications.

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