Imurel (Azathioprine)

Azathioprine is used in immunologic and inflammatory disease pathways to modulate immune activity.

• Organ transplant rejection: helps prevent graft rejection by suppressing lymphocyte proliferation.
• Rheumatoid arthritis: reduces joint inflammation and disease progression in patients with active disease.
• Inflammatory bowel disease: induces and maintains remission in Crohn’s disease and ulcerative colitis.

• Azathioprine is an antimetabolite that is converted intracellularly to 6‑mercaptopurine and subsequently to thioguanine nucleotides. These metabolites incorporate into DNA and RNA, inhibiting purine synthesis and thereby blocking the proliferation of rapidly dividing cells, particularly activated T and B lymphocytes. The resulting reduction in lymphocyte numbers dampens the immune response that drives transplant rejection and autoimmune inflammation.

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

Common Side Effects

• Nausea: mild gastrointestinal upset often occurring after dosing.
• Vomiting: occasional episodes of stomach upset.
• Diarrhea: loose stools that may be transient.
• Fatigue: general tiredness or lack of energy.
• Elevated liver enzymes: mild, reversible changes in hepatic function tests.
• Decreased white blood cell count: mild leukopenia detectable on routine labs.

Serious or Rare Side Effects

• Severe bone marrow suppression: pancytopenia requiring medical intervention.
• Hepatotoxicity: significant liver injury with jaundice or elevated transaminases.
• Increased risk of infections: opportunistic infections due to immunosuppression.
• Malignancies: higher incidence of lymphomas and skin cancers with long‑term use.
• Pancreatitis: acute inflammation of the pancreas presenting with abdominal pain.

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

• Baseline monitoring: obtain complete blood count and liver function tests prior to treatment.
• Ongoing monitoring: regularly assess blood counts and hepatic enzymes during therapy.
• Infection risk: avoid live vaccines and monitor for signs of infection.
• Renal impairment: adjust dose or increase monitoring in patients with reduced kidney function.
• Pregnancy and lactation: evaluate risks and benefits; use only if clearly indicated.
• Store at room temperature: keep tablets in the original container, protect from moisture and light.

Azathioprine interacts with several medicines; awareness of these interactions helps prevent toxicity or loss of efficacy.

Major Interactions (Avoid)

• Allopurinol or febuxostat: markedly increase azathioprine toxicity; concurrent use is contraindicated.
• Warfarin: azathioprine may enhance anticoagulant effect, raising INR and bleeding risk.
• Live vaccines: combined immunosuppression can lead to severe infection.

Moderate Interactions (Monitor Closely)

• NSAIDs: may further impair renal function and increase gastrointestinal irritation.
• Sulfonamide antibiotics: can add to bone marrow suppression.
• ACE inhibitors or ARBs: may potentiate renal effects, requiring closer monitoring of kidney function.