TRISENOX, with its active ingredient arsenic trioxide, is a chemotherapeutic agent primarily used in the treatment of acute promyelocytic leukemia (APL), a subtype of acute myeloid leukemia characterized by the accumulation of abnormal promyelocytes. Arsenic trioxide works by inducing apoptosis (programmed cell death) and partially through causing differentiation of the leukemic cells back into normal cells. It is administered intravenously and is known for its effectiveness in patients who have relapsed or are refractory to initial treatment. Despite its efficacy, TRISENOX can have significant side effects, and its use requires careful monitoring of the patient's cardiac function, electrolyte levels, and blood counts.