Mercaptopurine — also known as 6-MP — is a medicine used mainly in the maintenance phase of treatment for acute lymphoblastic leukaemia (ALL), a cancer that affects white blood cells. Maintenance therapy is the longest phase of ALL treatment, typically lasting two to three years. Its goal is to keep the cancer from returning after earlier treatment has put it into remission.
Mercaptopurine works by disrupting the ability of abnormal cells to copy their DNA, slowing their growth and helping to prevent relapse. It is taken by mouth, usually as a once-daily tablet.
Your oncology team will prescribe the exact dose based on your body surface area, blood counts, and genetic test results — particularly TPMT and NUDT15 enzyme activity. Never adjust your dose without speaking to your doctor first.
This page provides educational information to help you and your family understand this medicine. It does not replace the guidance of your oncologist or treatment team.