Mercaptopurine is a medication primarily used to treat certain types of cancer, particularly leukemia. It works by interfering with the growth of cancer cells, slowing their proliferation, and ultimately leading to cell death. This drug is often part of a combination therapy to enhance its effectiveness. Patients taking Mercaptopurine may experience side effects, including nausea, vomiting, and an increased risk of infections due to its impact on the immune system. Regular monitoring by healthcare professionals is essential to manage these side effects and adjust dosages as needed for optimal treatment outcomes.