Imurel (Azathioprine)

Azathioprine is an immunosuppressive agent used in several chronic immune‑mediated conditions.

• Organ transplantation: reduces risk of graft rejection by inhibiting lymphocyte proliferation.
• Rheumatoid arthritis: decreases joint inflammation and slows disease progression.
• Inflammatory bowel disease: helps maintain remission in Crohn’s disease and ulcerative colitis.

• Azathioprine is a purine analog that is converted intracellularly to 6‑mercaptopurine, which interferes with de novo purine synthesis. By incorporating into DNA and RNA, it blocks the proliferation of rapidly dividing cells, particularly activated T and B lymphocytes, thereby dampening the immune response. The metabolite also inhibits the activity of enzymes involved in nucleotide salvage pathways, further reducing lymphocyte activation and cytokine production.

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

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset that may affect appetite.
• Fatigue: persistent tiredness that can interfere with daily activities.
• Elevated liver enzymes: mild hepatic changes detectable in routine blood tests.

Serious or Rare Side Effects

• Bone marrow suppression: anemia, leukopenia, or thrombocytopenia leading to increased infection risk.
• Severe infections: opportunistic bacterial, viral or fungal infections requiring prompt medical attention.
• Hepatotoxicity: significant liver injury that may present with jaundice or elevated transaminases.

When prescribing azathioprine, clinicians should consider several safety precautions to minimize risks.

• Baseline testing: obtain complete blood count and liver function tests before initiation.
• Monitoring: perform regular CBC and liver enzymes during therapy.
• Infection risk: avoid use in patients with active infections or immunodeficiency.
• Vaccination: ensure required vaccines are administered prior to starting treatment.
• Pregnancy and lactation: assess risks and discuss alternatives with women of childbearing potential.
• Store at ambient temperature: keep tablets in original container, protect from moisture and light.

Azathioprine interacts with several medicines that can alter its efficacy or safety profile.

Major Interactions (Avoid)

• Allopurinol: can increase azathioprine toxicity; dose reduction or avoidance required.
• Warfarin: may enhance anticoagulant effect, increasing bleeding risk.
• Live vaccines: concurrent use may cause severe infection.

Moderate Interactions (Monitor Closely)

• Ribavirin: may augment bone marrow suppression.
• Mycophenolate mofetil: additive immunosuppression increasing infection risk.
• ACE inhibitors: possible increase in renal toxicity.