Mercaptopurine Accord (Mercaptopurine Monohydrate)

• Mercaptopurine acts on rapidly dividing cells by interfering with purine synthesis, making it useful in several hematologic and immune‑mediated conditions.
• Acute lymphoblastic leukemia (maintenance therapy): helps maintain remission in pediatric and adult patients.
• Inflammatory bowel disease (Crohn's disease, ulcerative colitis): reduces intestinal inflammation and supports remission.
• Chronic myeloid leukemia (off‑label): may be incorporated into experimental treatment protocols.

• Mercaptopurine is converted intracellularly to thio‑inosine monophosphate, which blocks de novo purine synthesis and becomes incorporated into DNA and RNA. This disruption of nucleic acid formation leads to cytotoxicity in rapidly proliferating cells such as leukemic blasts and activated lymphocytes, providing antineoplastic and immunosuppressive effects.

Mercaptopurine may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Nausea and vomiting
• Diarrhea or abdominal discomfort
• Loss of appetite
• Mild leukopenia or neutropenia
• Rash or mild skin irritation
• Fatigue or malaise

Serious or Rare Side Effects

• Severe bone marrow suppression (pancytopenia)
• Hepatotoxicity (elevated liver enzymes, hepatitis)
• Pancreatitis
• Severe infections due to immunosuppression
• Hypersensitivity reactions (including Stevens‑Johnson syndrome)
• Secondary malignancies (e.g., therapy‑related leukemia)

• When using Mercaptopurine, clinicians should observe several safety measures to minimize risks.
• Baseline blood counts: obtain a complete blood count before initiation.
• Liver function monitoring: assess hepatic enzymes regularly.
• Renal function: evaluate creatinine clearance in patients with kidney disease.
• Drug interactions: avoid concurrent use with allopurinol without dose adjustment.
• Pregnancy and lactation: consider risks versus benefits; use only if clearly needed.
• Store at room temperature: keep in the original container, protect from moisture and light.

Mercaptopurine interacts with several medicines that can alter its efficacy or toxicity.

Major Interactions (Avoid)

• Allopurinol: can markedly increase Mercaptopurine levels, raising risk of bone marrow suppression.
• Azathioprine: combined use leads to additive myelosuppression.
• Warfarin: may enhance anticoagulant effect.

Moderate Interactions (Monitor Closely)

• TPMT inhibitors (e.g., furosemide): may affect metabolism and increase toxicity.
• Fluoroquinolones: can increase risk of neutropenia.
• Methotrexate: may potentiate myelosuppression.