How it is administered

Mercaptopurine is taken by mouth, either as a tablet or as an oral suspension (liquid). Tablets are usually 50 mg and are swallowed whole. The oral suspension contains 20 mg/mL and should be shaken well before use. The medication should be taken consistently with or without food, as advised by your healthcare provider. Special care should be taken in handling and measuring the oral suspension, and it should be used within 8 weeks of opening.

How it works

Mercaptopurine is a type of chemotherapy called a nucleoside metabolic inhibitor. It works by interfering with the growth of cancer cells, specifically by acting as a purine analog. Once inside the body, mercaptopurine is converted into active metabolites, including thioguanine nucleotides (TGNs). These metabolites are incorporated into the DNA and RNA of cells, which disrupts their normal function and leads to cell-cycle arrest and cell death.

Mercaptopurine also inhibits the synthesis of new purines, which are essential building blocks for DNA and RNA. By blocking these processes, mercaptopurine slows down or stops the growth of rapidly dividing cells, such as those found in certain types of blood cancers. The medication is especially effective against cells that are actively dividing, which is why it is used as part of maintenance therapy for blood cancers like acute lymphoblastic leukemia (ALL).

Who Should take it

Mercaptopurine is indicated for adults and children with acute lymphoblastic leukemia (ALL) as part of a combination chemotherapy maintenance regimen. It is used after initial treatment to help keep leukemia in remission and prevent it from returning.

Your doctor may prescribe mercaptopurine if you are in the maintenance phase of ALL treatment. It is important to take the medication exactly as prescribed and to attend regular follow-up appointments for monitoring, as the dose may need to be adjusted based on your blood counts and how you tolerate the medication.

Who should not take it

There are no absolute contraindications listed for mercaptopurine, but certain people should use it with caution or may need dose adjustments. Patients with severe myelosuppression (very low blood cell counts), liver impairment, or kidney impairment may require lower doses or closer monitoring.

Mercaptopurine can cause harm to an unborn baby, so it should not be used during pregnancy unless clearly needed. Women of childbearing potential should use effective contraception during treatment and for 6 months after the last dose. Men with female partners should use contraception during treatment and for 3 months after the last dose. Breastfeeding is not recommended during treatment and for 1 week after the last dose.

Commonly used with

Mercaptopurine is most commonly used as part of a combination chemotherapy regimen for acute lymphoblastic leukemia (ALL). It is often used with other chemotherapy drugs such as methotrexate, vincristine, and corticosteroids (like prednisone or dexamethasone).

It may also be used with medications to help manage side effects, such as anti-nausea drugs. If you are taking allopurinol (a medication for gout), your doctor may need to lower your mercaptopurine dose, as allopurinol can increase the levels of mercaptopurine in your body.

Commonly tested with

Mercaptopurine is frequently tested in combination with other chemotherapy agents, especially methotrexate, as part of maintenance therapy for ALL. Studies often evaluate different dosing strategies and combinations to optimize effectiveness and minimize side effects.

Genetic testing for TPMT and NUDT15 enzyme activity may be performed before or during treatment to help determine the safest and most effective dose for each patient, as deficiencies in these enzymes can increase the risk of severe side effects.