Imatib 400 Tablet is used to treat several types of cancers. It is most commonly prescribed to treat blood cancers (chronic myeloid leukemia and acute lymphocytic leukemia) and gastrointestinal stromal tumors. It works by targeting specific proteins that contribute to the growth and spread of cancer cells. Imatib 400 Tablet is also used for treatment of a skin tumor called dermatofibrosarcoma protuberans and a type of bone marrow condition called aggressive systemic mastocytosis. The medicine should be taken with food. Take it at the same time each day to get the most benefit. Continue taking it as long as your doctor advises for it. The duration of treatment varies according to your need and response to treatment. Taking it in the wrong way or taking too much can cause very serious side effects. It may take several weeks or months for you to see or feel the benefits but do not stop taking it unless your doctor tells you to. The most common side effects of this medicine include edema, nausea, vomiting, muscle cramps, musculoskeletal pain, diarrhea, rash, fatigue, and abdominal pain. Let your doctor know if you experience unexpected rapid weight gain. Your doctor may advise for regular monitoring of blood cells and liver function while you are taking this medicine. Do not drive or do anything requiring mental focus if you experience dizziness and blurry vision. Many other medicines can affect, or be affected by, this medicine so let your healthcare team know all medications you are using. This medicine is not recommended during pregnancy or while breastfeeding. The use of effective contraception by both males and females during treatment is important to avoid pregnancy.