General
Description & Use
Used to treat leukemia. Also is used to treat many types of autoimmune
diseases such as systemic lupus erythematosus, rheumatoid arthritis,
acute idiopathic polyneuritis, acute idiopathic nephrotic syndrome,
psoriatic arthritis, erythroid aplasia, or idiopathic pulmonary
hemosiderosis, colon cancer; multiple sclerosis; and ulcerative
colitis.
Mercaptopurine
(also called 6-Mercaptopurine, 6-MP or its brand name Purinethol)
is an immunosuppressive drug (cancer drug) used to treat leukemia.
It is also used for pediatric non-Hodgkin's lymphoma, polycythemia
vera, psoriatic arthritis, and inflammatory bowel disease (such
as Crohn's Disease and ulcerative colitis). Mercaptopurine is
converted to the corresponding ribonucleotide. 6-MP ribonucleotide
inhibits purine nucleotide synthesis and metabolism. This alters
the synthesis and function of RNA and DNA.
Also
see under 6-MP
Mercaptopurine
interferes with nucleotide interconversion and glycoprotein synthesis.
Adverse
reactions
Some of the adverse reactions of taking Mercaptopurine might include
diarrhea, nausea, vomiting, loss of appetite, stomach/abdominal
pain, weakness, skin rash, darkening of the skin, or hair loss.
Serious adverse reactions include mouth sores, fever, sore throat,
easy bruising or bleeding, pinpoint red spots on the skin, yellowing
of eyes or skin, dark urine, painful or difficult urination. Unlikely
but serious side effects include: black or tarry stools (melena),
bloody stools, and bloody urine. Symptoms of allergic reaction
to Mercaptopurine include rash, itching, swelling, dizziness,
trouble breathing. Mercaptopurine causes myelosuppression, suppressing
the production of white blood cells and red blood cells. It may
be toxic to bone marrow. Weekly blood counts are recommended for
patients on mercaptopurine. The patient should stop taking the
medication at least temporarily if there is an unexplained, abnormally
large drop in white blood cell count, or any other blood count.
Patients who exhibit myelosuppression or bone marrow toxicity
should be tested for Thiopurine methyltransferase (TPMT) enzyme
deficiency. Patients with TPMT deficiency are much more likely
to develop dangerous myelosuppression. In such patients it may
be possible to continue using mercaptopurine, but at a lower dose.
Drug
Interactions
Allopurinol inhibits xanthine oxidase, the enzyme that breaks
down mercaptopurine. Those who take allopurinol (often used to
prevent gout) are at a risk mercaptopurine toxicity. The dose
should be reduced or allopurinol should be discontinued.
Precautions
Mercaptopurine can lower the body's ability to fight off infection.
Those taking mercaptopurine should get permission from a doctor
in order to receive immunizations and vaccinations. It is also
recommended that while on the drug one should avoid those who
have recently received oral polio vaccine. This drug is traditionally
not recommended during pregnancy but this issue has been debated
and current evidence indicates that pregnant women on the drug
show no increase in fetal abnormalities. However, women receiving
mercaptopurine during pregnancy have an increased incidence of
abortion.
