Za Pharmacy
Drugs, Supplies and Delivery
Azathioprine
Azathioprine is an immunosuppressive medication widely used to prevent organ transplant rejection and to treat autoimmune diseases such as rheumatoid arthritis, inflammatory bowel disease (IBD), and systemic lupus erythematosus (SLE). It is a prodrug that is metabolized to its active form, 6-mercaptopurine (6-MP), which inhibits purine synthesis and suppresses immune cell proliferation. This article synthesizes information from the British National Formulary (BNF), Lippincott Textbook of Pharmacology, and Lange Basic & Clinical Pharmacology to provide a detailed overview of azathioprine, including its mechanism, uses, dosing, side effects, precautions, and drug interactions
Azathioprine is metabolized in the liver to 6-mercaptopurine (6-MP), which is further converted to active metabolites such as 6-thioguanine nucleotides (6-TGN). These metabolites:
Inhibit purine synthesis: Interfere with DNA and RNA production, suppressing the proliferation of rapidly dividing cells, including immune cells (Lippincott, Lange).
Modulate immune response: Reduce the activity of T and B lymphocytes, thereby suppressing the immune system and preventing organ rejection or autoimmune reactions (BNF).
Organ Transplantation:
Prevents rejection of kidney, liver, and heart transplants (BNF).
Inflammatory Bowel Disease (IBD):
Used to maintain remission in Crohn’s disease and ulcerative colitis (Lippincott).
Rheumatoid Arthritis:
Used as a disease-modifying antirheumatic drug (DMARD) in patients unresponsive to other therapies (Lange).
Systemic Lupus Erythematosus (SLE):
Manages severe or refractory cases (BNF).
Autoimmune Hepatitis:
Used to induce and maintain remission (Lippincott).
Adults:
Transplant Rejection: 1–3 mg/kg/day orally or intravenously, adjusted based on response and tolerance (BNF).
Autoimmune Diseases: 1–2.5 mg/kg/day orally, starting at the lower end of the range and titrating upward (Lippincott).
Children:
1–3 mg/kg/day orally or intravenously, adjusted based on weight and clinical response (Lange).
Administration:
Oral tablets should be taken with or after food to minimize gastrointestinal side effects.
Intravenous administration is reserved for patients unable to take oral medication (BNF).
Common: Nausea, vomiting, diarrhea, and fatigue (Lippincott).
Serious:
Bone Marrow Suppression: Leukopenia, thrombocytopenia, and anemia (Lange).
Hepatotoxicity: Elevated liver enzymes and rare cases of hepatic veno-occlusive disease (BNF).
Increased Infection Risk: Bacterial, viral, and fungal infections due to immunosuppression (Lippincott).
Malignancies: Long-term use may increase the risk of lymphoma and skin cancer (Lange).
Thiopurine Methyltransferase (TPMT) Deficiency: Screen for TPMT enzyme activity before starting therapy to avoid severe myelosuppression (BNF).
Pregnancy and Lactation: Use only if benefits outweigh risks; potential risk of fetal harm (Lippincott).
Liver or Kidney Impairment: Dose reduction may be necessary (Lange).
Hypersensitivity: Contraindicated in patients with known hypersensitivity to azathioprine or 6-mercaptopurine (BNF).
Allopurinol: Inhibits xanthine oxidase, increasing azathioprine toxicity; reduce azathioprine dose by 75% if co-administered (Lippincott).
Warfarin: Azathioprine may reduce the anticoagulant effect of warfarin (Lange).
Live Vaccines: Avoid concurrent use due to immunosuppression (BNF).
Angiotensin-Converting Enzyme (ACE) Inhibitors: Increased risk of leukopenia (Lippincott
Azathioprine is the generic name for this medication. It is marketed under the brand name Imuran®. Generic versions are widely available and cost-effective
