Imuran (Azathioprine)

Azathioprine is used to modulate immune‑mediated conditions by suppressing the proliferation of T‑ and B‑lymphocytes, thereby reducing pathological immune responses.

• Organ transplantation: helps prevent graft rejection by inhibiting activation and proliferation of T‑cells and B‑cells, supporting long‑term graft survival.
• Rheumatoid arthritis: reduces joint inflammation, pain, and structural damage by dampening the autoimmune response that drives synovial tissue destruction.
• Inflammatory bowel disease: maintains remission in Crohn’s disease and ulcerative colitis by limiting the overactive immune activity that causes intestinal inflammation.

These uses reflect the drug’s role in controlling aberrant immune activity across several serious conditions.

• Azathioprine is a pro‑drug that is converted intracellularly to 6‑mercaptopurine, which interferes with purine nucleotide synthesis. By inhibiting the formation of adenine and guanine nucleotides, it blocks DNA replication and reduces proliferation of rapidly dividing cells, particularly activated T‑ and B‑lymphocytes. This suppression of lymphocyte expansion diminishes the immune response that underlies graft rejection and chronic autoimmune inflammation in the body.

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

Common Side Effects

• Nausea: mild stomach upset or queasiness that may improve with food.
• Vomiting: occasional episodes of expulsion that can lead to dehydration if persistent.
• Diarrhea: loose stools that may be accompanied by abdominal cramping.
• Fatigue: general tiredness or lack of energy affecting daily activities.
• Elevated liver enzymes: mild hepatic enzyme rise detected in routine laboratory tests, usually without symptoms.

Serious or Rare Side Effects

• Bone marrow suppression: decreased production of red cells, white cells, or platelets, leading to anemia, leukopenia, or thrombocytopenia.
• Severe infections: opportunistic bacterial, viral or fungal infections due to reduced immune defenses.
• Hepatotoxicity: significant liver injury or hepatitis presenting with jaundice, abdominal pain, or abnormal labs.
• Pancreatitis: inflammation of the pancreas causing severe abdominal pain, nausea and elevated enzymes.
• Malignancy risk: increased chance of lymphomas, leukemias or skin cancers with long‑term therapy.

Before prescribing azathioprine, clinicians should consider several precautionary measures to ensure patient safety.

• Baseline testing: obtain complete blood count, liver function tests and renal function before initiation.
• Monitoring: perform regular CBC and liver enzyme assessments during therapy to detect toxicity early.
• Infection risk: avoid use in patients with active infections and vaccinate appropriately before treatment.
• Pregnancy and lactation: assess risks and discuss potential teratogenic effects; use only if benefits outweigh risks.
• Drug interactions: review concomitant medications that may increase azathioprine levels or toxicity.
• Store at ambient temperature: keep tablets in the original container, protect from moisture and heat, and store below 25 °C.

Azathioprine interacts with several medicines that can alter its effectiveness or increase toxicity.

Major Interactions (Avoid)

• Allopurinol and febuxostat: potentiate azathioprine toxicity by inhibiting its metabolism.
• Mycophenolate mofetil: combined immunosuppression may cause severe bone marrow suppression.
• High‑dose ribavirin: increases risk of hematologic adverse effects.

Moderate Interactions (Monitor Closely)

• Warfarin: azathioprine may enhance anticoagulant effect, requiring INR monitoring.
• ACE inhibitors or ARBs: may affect renal function; monitor kidney parameters.
• Live vaccines: reduced efficacy and increased infection risk; avoid during therapy.