What Is Mercaptopurine Used For?
Adults and children who have a type of cancer called acute lymphatic leukemia may receive a medication called mercaptopurine. This prescription drug works by interfering with the multiplication process of cancer cells. Mercaptopurine may also be used off-label to treat other conditions, such as acute myelogenous leukemia, ulcerative colitis, and non-Hodgkin's lymphoma.
Mercaptopurine (Purinethol®) is a prescription medication approved for the treatment of acute lymphatic leukemia (ALL), also called acute lymphocytic or acute lymphoblastic leukemia. It belongs to a group of medicines known as purine analogs.
ALL is a type of cancer of the blood and bone marrow. It occurs when the bone marrow (the spongy interior of most bones) produces too many lymphocytes, which are a type of white blood cell.
The lymphocytes in ALL, called leukemia cells, are abnormal, and do not function like normal lymphocytes. They also grow quickly. As they build up, the leukemia cells crowd out the normal, healthy red blood cells, white blood cells, and platelets. As a result, a person with ALL is at risk for anemia, infections, and bleeding, which can lead to a variety of symptoms (see Symptoms of ALL for more information about specific symptoms that may occur).
No one knows the exact cause of acute lymphocytic leukemia, and doctors can seldom explain why one person will get ALL and another person will not. ALL is the most common type of leukemia in children; however, it also occurs in adults.
In general, treatment for ALL can be divided into three phases, which include:
- Maintenance therapy.
The goal of the first phase, induction therapy, is to kill the leukemia cells in the blood and bone marrow and put the leukemia into remission. Treatment in this phase normally includes chemotherapy and is almost always carried out in the hospital.
Once there are no detectable leukemia cells in the blood or bone marrow and the bone marrow is functioning normally, a person is said to be in remission. However, some abnormal cells may still be present, escaping detection. Therefore, additional treatment is normally needed even after remission to prevent these lingering leukemia cells from causing a relapse (a recurrence of ALL).
The purpose of the second phase of treatment, consolidation/intensification therapy, is to kill any remaining leukemia cells that may not be active but that could begin to regrow and cause a relapse. This phase of treatment often lasts several months. Treatment can usually take place during the day, preventing the need for hospitalization.
The last phase of treatment, maintenance therapy, is used to prevent leukemia cells from regrowing. In most cases, cancer treatments are given in lower doses during maintenance therapy, thus reducing the intensity of treatment side effects. Treatment often continues for several years.
ALL can sometimes spread to the central nervous system (the brain and spinal cord). However, chemotherapy that is given by mouth or injected into a vein may not reach leukemia cells in the brain and spinal cord. Therefore, in addition to standard chemotherapy, each phase of treatment may also require treatment with radiation therapy or an injection of chemotherapy directly into the fluid surrounding the brain and spinal cord.
Mercaptopurine is approved for the maintenance treatment of ALL, in combination with other treatments. It is not effective in preventing ALL from spreading to the central nervous system and will not treat central nervous system leukemia.