Imuran (Azathioprine)

Azathioprine is used to modulate immune activity in several autoimmune and transplant‑related conditions.

• Organ transplant rejection: helps prevent graft rejection by suppressing lymphocyte proliferation and reducing immune‑mediated damage to the transplanted organ.
• Rheumatoid arthritis: reduces joint inflammation, pain, and structural damage, providing disease‑modifying benefits in patients with moderate to severe disease.
• Inflammatory bowel disease (Crohn's disease, ulcerative colitis): maintains remission, decreases intestinal inflammation, and lowers the frequency of flare‑ups.
• Systemic lupus erythematosus: controls disease activity by limiting auto‑immune attacks on skin, kidneys, and other organs, helping to prevent flares.

• Azathioprine is a prodrug that is converted intracellularly to 6‑mercaptopurine, which interferes with purine nucleotide synthesis. By inhibiting the formation of adenine and guanine bases, it reduces DNA and RNA production, particularly affecting rapidly dividing lymphocytes. This suppression of lymphocyte proliferation diminishes the immune response, providing immunosuppressive effects useful in transplant and autoimmune conditions. The drug also impairs the activation of T‑cells and B‑cells, further contributing to its immunomodulatory profile.

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

Common Side Effects

• Nausea: mild stomach upset or vomiting.
• Hair loss: thinning or temporary loss of scalp hair.
• Increased susceptibility to infections: more frequent colds or respiratory infections.
• Elevated liver enzymes: mild changes detected in blood tests.

Serious or Rare Side Effects

• Bone marrow suppression: anemia, leukopenia, or thrombocytopenia requiring monitoring.
• Severe infections: opportunistic infections such as pneumonia or sepsis.
• Pancreatitis: abdominal pain with elevated enzymes.
• Liver toxicity: hepatitis or hepatic failure in rare cases.

Before initiating azathioprine therapy, several precautions should be observed to ensure patient safety.

• Baseline testing: obtain complete blood count and liver function tests prior to treatment.
• Monitoring: perform regular CBC and liver enzymes to detect hematologic or hepatic toxicity.
• Infection risk: avoid use in patients with active infections and vaccinate before starting when possible.
• Drug interactions: review concomitant medications that may enhance myelosuppression, such as allopurinol.
• Pregnancy and lactation: assess risks and discuss with a specialist; use only if benefits outweigh risks.
• Store at ambient temperature: keep tablets in original container, protect from moisture and heat, and store below 25 °C.

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

Major Interactions (Avoid)

• Allopurinol: may markedly increase azathioprine toxicity; concurrent use generally avoided.
• Warfarin: azathioprine can enhance anticoagulant effect, requiring close INR monitoring.
• Live vaccines: increased risk of infection; avoid administration during therapy.

Moderate Interactions (Monitor Closely)

• Rifampin: may reduce azathioprine levels, decreasing effectiveness.
• Sulfasalazine: can increase risk of bone marrow suppression.
• ACE inhibitors: may potentiate renal effects; monitor renal function.