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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Other
Imatinib is a potent tyrosine kinase inhibitor used as a targeted therapy for certain cancers, including Chronic Myeloid Leukemia (CML) and Gastrointestinal Stromal Tumors (GIST), by blocking specific growth-signaling proteins.
Name
Imatinib
Raw Name
IMATINIB MESYLATE
Category
Other
Salt Form
Mesylate
Drug Count
6
Variant Count
46
Last Verified
February 17, 2026
RxCUI
2699831, 2699837, 403878, 403879, 404588, 404589
UNII
8A1O1M485B
About Imatinib
Imatinib is a potent tyrosine kinase inhibitor used as a targeted therapy for certain cancers, including Chronic Myeloid Leukemia (CML) and Gastrointestinal Stromal Tumors (GIST), by blocking specific growth-signaling proteins.
Detailed information about Imatinib
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Imatinib.
Clinically, imatinib is often referred to as a 'signal transduction inhibitor.' This means it interrupts the communication pathways that tell a cancer cell to grow and divide. By blocking these signals, imatinib can lead to the death of the cancer cell or prevent it from spreading. It is most famously used to treat Philadelphia chromosome-positive (Ph+) Chronic Myeloid Leukemia (CML), a condition where a genetic swap between chromosomes 9 and 22 creates an abnormal protein called Bcr-Abl. Your healthcare provider will typically perform genetic testing to confirm the presence of these targets before initiating therapy.
At the molecular level, imatinib works by binding to the adenosine triphosphate (ATP) binding site of specific tyrosine kinase enzymes. In many cancers, these enzymes are mutated or overactive, essentially acting like a 'stuck switch' that remains in the 'on' position, constantly sending growth signals. Imatinib specifically targets three main proteins: the Bcr-Abl tyrosine kinase, the c-KIT (CD117) receptor tyrosine kinase, and the Platelet-Derived Growth Factor Receptors (PDGFR).
In Chronic Myeloid Leukemia (CML), the Bcr-Abl protein is the primary driver of the disease. Imatinib occupies the ATP-binding pocket of this protein, preventing it from transferring a phosphate group to its substrate. Without this phosphorylation (the chemical process of adding a phosphate), the downstream signaling cascade required for cell proliferation and survival is halted. Similarly, in Gastrointestinal Stromal Tumors (GIST), imatinib inhibits the mutated c-KIT or PDGFR enzymes, which are responsible for the uncontrolled growth of these soft tissue tumors. This high degree of specificity allows imatinib to be remarkably effective while sparing many healthy cells, though side effects still occur due to the inhibition of these proteins in normal tissues.
Understanding how the body processes imatinib is crucial for maximizing its efficacy and minimizing toxicity. The pharmacokinetic profile of imatinib is characterized by high oral bioavailability and a predictable metabolic pathway.
Imatinib is FDA-approved for a wide range of conditions, often depending on the specific genetic profile of the tumor. Common uses include:
Imatinib is primarily available in oral tablet form. It is most commonly found in strengths of 100 mg and 400 mg. The tablets are film-coated to protect the active ingredient and are designed to be swallowed whole. For patients who have difficulty swallowing, some formulations may be dispersed in water or apple juice, but this must be done strictly according to the manufacturer's instructions and under medical supervision. There are currently no approved injectable or liquid-only versions of imatinib available on the market.
> Important: Only your healthcare provider can determine if Imatinib is right for your specific condition. Treatment decisions are based on genetic testing, the stage of your disease, and your overall health status.
The dosage of imatinib is highly individualized and depends on the specific condition being treated, the phase of the disease, and the patient's response to therapy. According to clinical guidelines:
Imatinib is approved for use in children with Ph+ CML in the chronic phase and newly diagnosed Ph+ ALL (in combination with chemotherapy). Dosing in children is usually based on body surface area (BSA):
There is limited data on the use of imatinib in children under the age of 2 for CML and under the age of 1 for ALL. Growth monitoring is essential in pediatric patients, as imatinib has been associated with growth retardation in some children.
Since imatinib is not primarily cleared by the kidneys, dose adjustments for mild renal impairment are often not necessary. However, for patients with moderate renal impairment (Creatinine Clearance 20-39 mL/min), a 25% dose reduction is typically recommended. Imatinib should be used with extreme caution in patients with severe renal failure or those on dialysis.
Because imatinib is metabolized by the liver, patients with mild, moderate, or severe hepatic impairment should be monitored closely. For patients with severe hepatic impairment, a dose reduction of 25% is generally recommended (e.g., reducing a 400 mg dose to 300 mg). Liver function tests (LFTs) must be performed before starting treatment and monthly thereafter.
No specific dose adjustments are required based solely on age. However, elderly patients are at a higher risk of developing fluid retention and edema (swelling), as well as cardiac complications. Close monitoring of weight and heart function is advised in patients over 65.
Imatinib should be taken orally with a meal and a large glass of water (approximately 8 ounces or 240 mL). This helps minimize the risk of gastrointestinal irritation, such as nausea or stomach pain. The tablets should generally be swallowed whole. If you cannot swallow the tablet, consult your pharmacist; some 100 mg or 400 mg tablets can be dissolved in water or apple juice. The resulting suspension must be consumed immediately. Avoid grapefruit and grapefruit juice, as they can increase the levels of imatinib in your blood to dangerous levels. Store the medication at room temperature, away from moisture and heat.
If you miss a dose of imatinib, skip the missed dose and take your next scheduled dose at the regular time. Do not take two doses at once to make up for a missed one. Consistency is vital for maintaining the 'molecular blockade' against cancer cells; if you frequently miss doses, the cancer may become resistant to the medication.
Symptoms of an imatinib overdose may include severe muscle cramps, vomiting, abdominal pain, and extreme fatigue. In the event of a suspected overdose, contact your local poison control center or seek emergency medical attention immediately. There is no specific antidote for imatinib; treatment involves supportive care and monitoring of vital signs.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or stop taking the medication without medical guidance, as this can lead to disease progression.
Imatinib is generally better tolerated than traditional chemotherapy, but most patients will experience some side effects. The most common include:
> Warning: Stop taking Imatinib and call your doctor immediately if you experience any of these.
With prolonged use, some patients may develop chronic issues. These can include:
As of 2026, Imatinib does not carry an FDA Black Box Warning. However, it does carry significant 'Warnings and Precautions' regarding fluid retention, hematologic toxicity, and hepatotoxicity that are considered nearly as critical for patient safety.
Report any unusual symptoms to your healthcare provider immediately. Most side effects are manageable with supportive care or dose modifications.
Imatinib is a high-potency medication that requires careful clinical oversight. It is not a 'set and forget' treatment; it requires ongoing communication between the patient and a multidisciplinary medical team (oncologist, hematologist, pharmacist). Patients must be aware that while imatinib is highly effective, it can cause significant internal changes that may not be immediately felt, such as shifts in blood counts or liver enzyme elevations.
No FDA black box warnings for Imatinib. However, the FDA emphasizes that severe, life-threatening toxicities can occur, particularly involving the liver, heart, and skin.
Effective management of imatinib therapy requires a strict monitoring schedule:
Imatinib may cause dizziness, blurred vision, or fatigue in some patients. You should not drive or operate heavy machinery until you know how the medication affects you. If you experience significant lightheadedness, avoid these activities and consult your doctor.
There is no absolute contraindication against moderate alcohol use with imatinib. However, because both imatinib and alcohol are processed by the liver, excessive alcohol consumption can increase the risk of hepatotoxicity (liver damage). It is generally advised to limit alcohol intake while on this medication.
Never stop taking imatinib abruptly without consulting your oncologist. In some CML patients who have achieved a 'deep molecular response' for several years, a supervised 'Treatment-Free Remission' (TFR) trial may be considered. However, this involves extremely frequent monitoring (monthly PCR tests) because the risk of the leukemia returning is high. If stopped without supervision, the cancer can rapidly return and potentially develop resistance to the drug.
> Important: Discuss all your medical conditions, including any history of heart, liver, or kidney disease, with your healthcare provider before starting Imatinib.
While few drugs are strictly 'never use,' certain combinations are so risky they are generally avoided:
Imatinib does not typically interfere with the chemical assays used in standard lab tests, but its physiological effects will change the results. For example, it will lower white blood cell counts and may increase serum bilirubin. It is important that the lab and your doctors know you are on a TKI so they can interpret these 'abnormal' results correctly in the context of your treatment.
For each major interaction, the management strategy usually involves:
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. Even 'natural' products can have life-threatening interactions with imatinib.
There are very few absolute contraindications for imatinib, given its life-saving nature in cancer treatment. However, the following apply:
These are conditions where the benefit of treating the cancer must be carefully weighed against the risks:
There is no known cross-sensitivity between imatinib and traditional chemotherapy agents. However, there may be cross-sensitivity with other tyrosine kinase inhibitors (TKIs) like dasatinib, nilotinib, or bosutinib. If a patient develops a severe skin rash on imatinib, they may be at a higher risk of a similar reaction with other TKIs, though this is not guaranteed.
> Important: Your healthcare provider will evaluate your complete medical history, including any prior drug allergies and organ function, before prescribing Imatinib. Always disclose any history of hepatitis or heart disease.
Imatinib is classified as a pregnancy risk (formerly FDA Category D). Data from animal studies and human case reports indicate that imatinib can cause fetal harm when administered to a pregnant woman. Reported malformations include skull bone ossification defects, heart defects, and limb abnormalities.
Imatinib and its active metabolite are excreted in human milk. Because of the potential for serious adverse reactions in nursing infants (including myelosuppression and growth issues), breastfeeding is not recommended during treatment and for at least one month after the last dose. Mothers are encouraged to use formula or donor milk to ensure the safety of the infant.
Imatinib is approved for children with Ph+ CML and Ph+ ALL.
Clinical studies have shown that the efficacy of imatinib in patients over 65 is similar to that in younger adults. However, geriatric patients are more likely to experience:
Imatinib is not significantly cleared by the kidneys, but renal impairment can affect the protein binding of the drug.
Since the liver is the primary site of metabolism, hepatic impairment significantly increases drug exposure.
> Important: Special populations require individualized medical assessment. Never start or stop imatinib in these populations without expert oncological consultation.
Imatinib is a small-molecule protein kinase inhibitor. Its primary target is the Bcr-Abl tyrosine kinase, an abnormal enzyme produced by the Philadelphia chromosome (a translocation between chromosomes 9 and 22). In the absence of the drug, Bcr-Abl binds ATP and transfers a phosphate group to tyrosine residues on substrate proteins. This phosphorylation triggers a cascade of signals (including the PI3K/Akt and Ras/MAPK pathways) that lead to uncontrolled cell division and resistance to apoptosis (programmed cell death).
Imatinib acts as a competitive inhibitor; it sits in the ATP-binding pocket of the Bcr-Abl protein, specifically when the protein is in its 'inactive' conformation. By blocking ATP from binding, it prevents the phosphorylation of substrates, effectively 'starving' the cancer cell of the signals it needs to survive. Imatinib also inhibits the c-KIT receptor (stem cell factor receptor) and the Platelet-Derived Growth Factor Receptor (PDGFR), which are critical in the pathogenesis of GIST and certain other rare tumors.
The pharmacodynamic effect of imatinib is dose-dependent. Higher doses lead to more complete inhibition of the target kinases. In CML, the effectiveness is measured by the reduction in the number of cells containing the Philadelphia chromosome (cytogenetic response) and the reduction in the BCR-ABL1 transcript levels (molecular response). The onset of action is rapid, with molecular changes occurring within hours of the first dose, although clinical changes in blood counts may take 1-2 weeks.
| Parameter | Value |
|---|---|
| Bioavailability | 98% |
| Protein Binding | 95% (mainly Albumin and AGP) |
| Half-life | 18 hours (Parent), 40 hours (Metabolite) |
| Tmax | 2 to 4 hours |
| Metabolism | Hepatic (Primary: CYP3A4; Minor: CYP2C9, 2C19, 2D6) |
| Excretion | Fecal 81%, Renal 13% |
Imatinib is classified as a Tyrosine Kinase Inhibitor (TKI) and a member of the 2-phenylaminopyrimidine class. It is often grouped with 'First-Generation' TKIs. Related medications in the same therapeutic class (Second and Third-Generation TKIs) include Dasatinib, Nilotinib, Bosutinib, and Ponatinib. While these newer drugs can overcome certain mutations that make imatinib less effective, imatinib remains the gold-standard first-line therapy for many patients due to its long-term safety data.
Medications containing this ingredient
Common questions about Imatinib
Imatinib is a targeted therapy medication primarily used to treat certain types of cancer, most notably Chronic Myeloid Leukemia (CML) and Gastrointestinal Stromal Tumors (GIST). It works by blocking specific proteins called tyrosine kinases that signal cancer cells to multiply and grow. In addition to CML and GIST, it is FDA-approved for Philadelphia chromosome-positive Acute Lymphoblastic Leukemia (Ph+ ALL), Myelodysplastic diseases, and Dermatofibrosarcoma Protuberans. Because it targets specific genetic mutations, it is often more effective and less toxic than traditional chemotherapy. Your doctor will use genetic testing to ensure your cancer has the specific markers that imatinib targets.
The most frequently reported side effects of imatinib include fluid retention (edema), nausea, muscle cramps, and fatigue. Many patients notice puffiness around the eyes or swelling in the ankles, which is a result of the drug's effect on blood vessel permeability. Gastrointestinal upset, such as diarrhea or vomiting, is also common but can often be managed by taking the medication with a full meal and a large glass of water. Some patients also experience a mild skin rash or bone pain during the first few months of treatment. Most of these side effects are mild to moderate and can be managed with supportive care or minor dose adjustments by your oncologist.
There is no direct, dangerous interaction between imatinib and moderate alcohol consumption, but caution is highly recommended. Both imatinib and alcohol are processed by the liver, so drinking alcohol can put extra strain on this organ and potentially increase the risk of liver toxicity. Since imatinib can cause side effects like dizziness and fatigue, alcohol may worsen these symptoms, making it unsafe to drive or perform tasks. It is best to limit your alcohol intake to occasional, small amounts and always discuss your habits with your healthcare provider. If your liver enzyme tests are elevated, your doctor will likely advise you to avoid alcohol entirely.
Imatinib is generally not considered safe during pregnancy and is known to cause birth defects and fetal harm. Studies in animals and reports in humans have shown that exposure to the drug during pregnancy can lead to serious skeletal and organ abnormalities in the developing fetus. Women of childbearing age must use effective contraception while taking imatinib and for at least two weeks after stopping the medication. If you are planning a pregnancy, you must discuss this with your oncologist, as they may suggest pausing treatment or switching to a different management strategy. Breastfeeding is also discouraged while taking imatinib because the drug passes into breast milk.
Imatinib begins working at the molecular level within hours of the first dose, but clinical results take longer to manifest. In patients with Chronic Myeloid Leukemia, white blood cell counts usually begin to normalize within the first 2 to 4 weeks of treatment, a stage called a complete hematologic response. Achieving a 'cytogenetic response,' where the Philadelphia chromosome is no longer detectable in the bone marrow, typically takes 3 to 6 months. A 'deep molecular response' can take a year or longer of consistent daily use. Your healthcare team will monitor your progress through regular blood tests and bone marrow biopsies to ensure the drug is effectively suppressing the cancer.
You should never stop taking imatinib suddenly or without the direct supervision of your oncologist. Stopping the medication allows the tyrosine kinase proteins to become active again, which can lead to a rapid return of cancer cells and disease progression. In some cases, stopping and restarting the drug can lead to 'acquired resistance,' where the cancer mutates and the drug no longer works. While some patients who have been in deep remission for many years may be candidates for a 'Treatment-Free Remission' trial, this is a highly controlled medical process. Always follow your prescribed schedule to maintain the necessary levels of the drug in your system.
If you miss a dose of imatinib, you should take it as soon as you remember, provided it is not too close to your next scheduled dose. However, if it is almost time for your next dose, you should skip the missed one and return to your regular schedule. Never take two doses at the same time to 'catch up,' as this significantly increases the risk of toxicity and side effects like severe nausea or fluid retention. To help remember your doses, it may be useful to use a pill organizer or a smartphone alarm. If you frequently miss doses, inform your doctor, as consistent levels of the medication are required to prevent the cancer from growing.
Weight gain is a common side effect of imatinib, but it is usually not caused by an increase in body fat. Instead, it is typically due to fluid retention, also known as edema. This fluid can accumulate in the legs, around the eyes, or even in the abdomen and around the lungs. While mild swelling is common, a sudden or rapid weight gain of more than 3 to 5 pounds in a single day can indicate a more serious complication like pleural effusion or heart strain. If you notice rapid weight gain or accompanying shortness of breath, you should contact your healthcare provider immediately. They may prescribe a diuretic (water pill) to help your body eliminate the excess fluid.
Imatinib has many potential drug interactions because it is processed by the CYP3A4 enzyme in the liver. Many common medications, including certain antibiotics, antifungals, and antiseizure drugs, can either increase or decrease the levels of imatinib in your blood. For example, St. John's Wort and Rifampin can make imatinib less effective, while Ketoconazole can make it more toxic. It can also interact with blood thinners like Warfarin, increasing the risk of dangerous bleeding. You must provide your doctor and pharmacist with a complete list of all prescription drugs, over-the-counter medicines, and herbal supplements you are taking to ensure your treatment is safe and effective.
Yes, imatinib is available as a generic medication and has been since the original patent for Gleevec expired. Generic imatinib is bioequivalent to the brand-name version, meaning it contains the same active ingredient and works in the same way within the body. Choosing the generic version can significantly reduce the cost of treatment, which is often a long-term or lifelong commitment for many patients. Most insurance plans cover generic imatinib, but you should verify this with your provider. Whether you take the brand-name or generic version, the monitoring requirements and potential side effects remain exactly the same.