How it is administered

Mercaptopurine is taken by mouth (orally). It is available as:

• Tablets (usually 50 mg per tablet)
• Oral suspension (liquid form, 20 mg/mL)

You should take mercaptopurine either consistently with or without food, as food can affect how much of the medication your body absorbs. If you are prescribed the oral suspension, shake the bottle well before use and use the provided oral syringe for accurate dosing.

How it works

Mercaptopurine is a type of chemotherapy known as a nucleoside metabolic inhibitor. It works by interfering with the growth of cancer cells, especially those that multiply quickly, such as blood cancer cells.

After entering the body, mercaptopurine is converted into active substances called thioguanine nucleotides (TGNs). These substances get incorporated into the DNA and RNA of cells, which disrupts the cell's ability to grow and divide. This leads to cell-cycle arrest and cell death, particularly in rapidly dividing cells like those found in leukemia.

Mercaptopurine also blocks the production of purines, which are building blocks needed for DNA and RNA synthesis. By stopping purine production, it further prevents cancer cells from multiplying. While the exact way mercaptopurine causes cancer cell death is not fully understood, its effects on DNA/RNA and purine synthesis are key to its action.

Who Should take it

Mercaptopurine is FDA-approved for the treatment of acute lymphoblastic leukemia (ALL) in both adults and children, as part of a combination chemotherapy maintenance regimen. While it is not specifically approved for Chronic Myelomonocytic Leukemia (CMML), it may sometimes be used in blood cancers where your doctor determines it could be beneficial.

If you have a blood cancer and your doctor prescribes mercaptopurine, it is usually because your cancer cells are sensitive to this type of chemotherapy. It is especially used in maintenance therapy to keep leukemia in remission after initial treatment.

Who should not take it

There are no absolute contraindications listed for mercaptopurine, but certain patients should use caution or avoid it:

• If you have a known hypersensitivity to mercaptopurine or any of its components, you should not take it.
• If you are pregnant or planning to become pregnant, mercaptopurine can harm the unborn baby and should only be used if clearly needed. Effective contraception is recommended during and after treatment.
• If you have severe liver or kidney problems, your doctor may need to adjust your dose or monitor you more closely.
• If you have a deficiency in certain enzymes (TPMT or NUDT15), you may be at higher risk for side effects and may need a lower dose.

Always discuss your full medical history with your doctor before starting mercaptopurine.

Commonly used with

Mercaptopurine is most often used as part of a combination chemotherapy regimen. It is commonly combined with other medications such as:

• Methotrexate
• Vincristine
• Prednisone or other corticosteroids
• Other chemotherapy agents, depending on the specific protocol

Your doctor will determine the best combination for your specific type of blood cancer.

Commonly tested with

Mercaptopurine is frequently tested in combination with other chemotherapy drugs, especially methotrexate, as this combination is standard in maintenance therapy for acute lymphoblastic leukemia. Studies often evaluate how mercaptopurine works with other agents to improve treatment outcomes and manage side effects.

If you are participating in a clinical trial or your doctor is considering a new combination, they may discuss other medications that are being tested with mercaptopurine.