Fexostat 40mg tablet is a drug belonging to the class of xanthine oxidase inhibitors, containing the active ingredient febuxostat. It is used to treat gout. A gout is a form of arthritis caused by excessive accumulation of uric acid in the body resulting in pain, tenderness, swelling, and difficulty moving the affected joint. Gout can occur in the toe joint, ears, heels, knees, wrists, and fingers. This medication is also used to prevent and treat high blood levels of uric acid, which may occur when you begin to receive chemotherapy for blood cancers. This drug decreases uric acid levels in the body, and it is also used in the prevention of TLS in patients. Tumour lysis syndrome (TLS) is a medical emergency that can occur in patients with certain types of cancer, particularly haematological malignancies such as leukaemia and lymphoma, who are undergoing chemotherapy. TLS can occur when cancer cells break down rapidly, releasing large amounts of intracellular contents such as uric acid, potassium, and phosphate into the bloodstream. During the treatment, your doctor may periodically monitor your white blood cell counts, platelets, blood sugar, electrolytes and kidney parameters to prevent serious complications. This medicine has the potential to cause heart problems. Inform the doctor if you have been diagnosed with liver disorders, heart failure, high blood cholesterol levels, or hypertension before starting this treatment. Report to your doctor if you experience any hypersensitive reactions like itchy skin or rashes while taking this medicine. This tablet contains lactose as an inactive ingredient in which the body is unable to digest lactose, a sugar found in milk and dairy products. It can cause symptoms such as bloating, and abdominal pain. If you have lactose intolerance, inform your doctor before starting this therapy.