Imatinib is an oral targeted medicine that transformed the treatment of chronic myeloid leukaemia (CML) by directly blocking the abnormal protein driving the disease. It belongs to a class of medicines called BCR-ABL tyrosine kinase inhibitors (TKIs), and remains a standard first-line treatment for CML, also used in certain other cancers including gastrointestinal stromal tumours (GIST). It is a prescription-only medicine.

Therapeutic Class: Anti-cancer (oncology) targeted therapy.

Pharmacological Class: BCR-ABL tyrosine kinase inhibitor (also inhibits KIT and PDGFR).

Drug Family: First-generation small-molecule tyrosine kinase inhibitors.

ATC Classification: L01EA01 (Imatinib).

Approved: Philadelphia chromosome-positive (Ph+) chronic myeloid leukaemia (CML) in chronic, accelerated, or blast phase, in adults and children; Philadelphia chromosome-positive acute lymphoblastic leukaemia (Ph+ ALL); KIT-positive gastrointestinal stromal tumours (GIST); and several other rarer conditions including certain myelodysplastic/myeloproliferative diseases, systemic mastocytosis, hypereosinophilic syndrome, and dermatofibrosarcoma protuberans.

Commonly used for: Patients with newly diagnosed or ongoing chronic-phase CML as first-line treatment, and patients with KIT-positive GIST, whether unresectable, metastatic, or as adjuvant therapy after surgery.

Off-label use (only under medical guidance): Occasionally used in other rare BCR-ABL-, KIT-, or PDGFR-driven conditions under specialist guidance.

• Oral tablets: 100 mg and 400 mg.

• Oral solution: for patients unable to swallow tablets.

In CML, a genetic change (the Philadelphia chromosome) creates an abnormal fusion protein called BCR-ABL, which acts as a constantly "switched on" growth signal, driving uncontrolled white blood cell production. Imatinib specifically blocks this BCR-ABL protein (and also inhibits related proteins KIT and PDGFR, relevant in GIST and other conditions), switching off the abnormal growth signal and allowing normal blood cell regulation to resume.

Standard dose (chronic-phase CML, adults): 400 mg orally once daily; may be increased to 600 mg or 800 mg (given as 400 mg twice daily) once daily in cases of disease progression or inadequate response.

Condition-wise dose (accelerated/blast-phase CML, adults): 600 mg orally once daily.

Condition-wise dose (children, newly diagnosed Ph+ CML): 340 mg/m2/day (not to exceed 600 mg), given once daily or split into two doses.

Route: Oral, taken with a meal and a large glass of water; tablets can be dispersed in water or apple juice for patients unable to swallow them whole.

Missed dose: Take as soon as remembered unless close to the next dose; don't double up — contact the treating team if unsure.

Overdose: May worsen known side effects such as fluid retention, low blood counts, or liver toxicity; requires medical attention.

Common: Fluid retention (swelling, particularly around the eyes and in the legs), nausea, diarrhoea, muscle cramps/pain (myalgia), rash, and fatigue.

Serious: Severe fluid retention (including pleural effusion or pulmonary edema in some cases), liver toxicity, significant low blood counts (neutropenia, thrombocytopenia), and, rarely, heart failure or gastrointestinal bleeding/perforation.

Emergency symptoms: Significant shortness of breath or swelling, yellowing of the skin/eyes, signs of serious infection (fever, chills) linked to low white cell counts, or severe abdominal pain.

Recovery advice: Mild fluid retention and muscle cramps are common and often manageable; regular blood counts and liver function tests allow more serious effects to be caught early and the dose adjusted if needed.

Pregnancy: Can cause fetal harm; effective contraception is recommended during treatment.

Breastfeeding: Not recommended during treatment.

Liver disease: Used with caution and monitoring; dose adjustment may be needed based on liver enzyme changes.

Kidney disease: Used with caution; dose adjustment may be needed in significant impairment.

Elderly: Used with routine monitoring; fluid retention effects may be more pronounced in this age group.

Children: Approved for pediatric Ph+ CML and Ph+ ALL, with body-surface-area-based dosing.

• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): can increase imatinib levels; used with caution.

• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine, St. John's Wort): can significantly reduce imatinib levels and effectiveness.

• Warfarin and other CYP3A4-metabolised, narrow-therapeutic-index drugs: imatinib can increase their levels, requiring dose adjustment; warfarin should generally be replaced with a low-molecular-weight or standard heparin if anticoagulation is needed.

• Acetaminophen (paracetamol): caution advised with regular or high-dose use given a theoretical increased risk of liver effects when combined with imatinib.

• Complete blood counts weekly for the first month, then every two weeks for the second month, then periodically thereafter.

• Liver function tests periodically.

• Monitoring for fluid retention (weight checks, symptom review).

• BCR-ABL molecular monitoring to track treatment response over time in CML.

Dasatinib, Nilotinib, Bosutinib, Asciminib (second- and third-generation BCR-ABL tyrosine kinase inhibitors, used first-line or after imatinib resistance/intolerance).

Used as monotherapy in most CML and GIST settings; sometimes combined with chemotherapy in Ph+ ALL treatment protocols, under specialist hematology-oncology guidance.

• Chronic Myeloid Leukaemia (CML) Medicines

• Gastrointestinal Stromal Tumour (GIST) Treatments

• BCR-ABL Tyrosine Kinase Inhibitors

1. Skin Rashes And Leukemia

2. Leukemia And Its Risk In Children Having Down Syndrome

• https://www.drugs.com/dosage/gleevec.html

• https://www.cancer.org/cancer/types/chronic-myeloid-leukemia/treating/targeted-therapies.html

The information on this page is for educational purposes only and is not a substitute for medical advice. Please consult your oncologist to know if this treatment is appropriate for your condition.