1. Introduction
Azathioprine, commonly marketed under the brand names Imuran and Azasan, is an immunosuppressive medication. It is primarily used to prevent organ rejection following transplantation and to treat autoimmune conditions by inhibiting purine synthesis, thus reducing the activity of immune cells.
2. Indications
- Approved Indications:
- Prevention of organ rejection in kidney transplant recipients.
- Management of rheumatoid arthritis.
- Off-Label Uses:
- Treatment of autoimmune diseases such as Crohn’s disease, ulcerative colitis, systemic lupus erythematosus (SLE), and myasthenia gravis.
3. Dosage
- Transplantation:
- Initial dose: 3–5 mg/kg/day orally, starting on the day of transplantation.
- Maintenance dose: 1–3 mg/kg/day.
- Rheumatoid Arthritis:
- Initial dose: 1 mg/kg/day orally.
- Maintenance dose: 1–3 mg/kg/day.
Dosage must be individualised based on patient response and blood counts.
4. Administration
- Administer orally, preferably with food to reduce gastrointestinal side effects.
- Tablets should be swallowed whole; do not crush or chew.
5. Forms Available
- Tablets: 25 mg, 50 mg.
6. Side Effects
6.1. Common Side Effects
- Nausea.
- Vomiting.
- Loss of appetite.
6.2. Less Common Side Effects
- Hair thinning.
- Skin rash.
- Diarrhoea.
6.3. Rare but Serious Side Effects
- Bone marrow suppression (leukopenia, thrombocytopenia, anaemia).
- Increased risk of infections.
- Hepatotoxicity.
- Malignancies (especially lymphoma and skin cancer).
7. Warnings
- Black Box Warning: Increased risk of malignancy, especially post-transplant lymphoma and skin cancer.
- Contraindicated in patients with known hypersensitivity to azathioprine.
- Avoid live vaccines during therapy.
8. Precautions
- Use with caution in patients with renal or hepatic impairment.
- Monitor for signs of bone marrow suppression (e.g., persistent infections, unusual bleeding).
- Genetic testing for TPMT (thiopurine methyltransferase) enzyme activity is recommended to identify patients at risk of severe myelosuppression.
9. Interactions
- Drug-Drug Interactions:
- Allopurinol, febuxostat: Increased risk of toxicity due to reduced metabolism of azathioprine.
- ACE inhibitors: Increased risk of anaemia and leukopenia.
- Warfarin: Reduced anticoagulant effect.
- Drug-Food Interactions:
- Avoid excessive intake of purine-rich foods as they may exacerbate gastrointestinal discomfort.
10. Monitoring Parameters
- Complete blood count (CBC) weekly during initial therapy, then monthly.
- Liver function tests (LFTs) regularly.
- Renal function periodically.
- Signs of infection or malignancy.
11. Use in Children
- Safety and efficacy have been established in paediatric transplantation.
- Dosage is weight-based, typically 1–3 mg/kg/day.
12. Use in Pregnancy
- Category D: Evidence of risk to the foetus.
- May be used if the potential benefit outweighs the risk, particularly in life-threatening conditions or organ transplantation.
- Women of childbearing age should use effective contraception during therapy.
13. Use in Elderly
- Use with caution due to increased susceptibility to infections and bone marrow suppression.
- Regular monitoring of renal and hepatic function is essential.
14. Use in Kidney Disease
- Dose adjustment may be required in patients with renal impairment.
- Regular monitoring of renal function is recommended.
15. Use in Liver Disease
- Use with caution in patients with hepatic impairment.
- Monitor liver enzymes frequently.
16. Patient Counselling Points
- Inform about the risk of infections and the need to report symptoms such as fever or unusual bleeding immediately.
- Advise regular blood tests to monitor therapy safety.
- Discuss the importance of using effective contraception during treatment.
- Avoid excessive sun exposure and use sunscreen to reduce the risk of skin cancer.
- Highlight the need to avoid live vaccines while on therapy.
17. Table of Brand Names, Manufacturers, and Prices
Brand Name | Manufacturer | Price (USD) |
---|---|---|
Imuran | Aspen Pharmacare | $50 (30 tablets, 50 mg) |
Azasan | Salix Pharmaceuticals | $60 (30 tablets, 50 mg) |
Generic Options | Various | $10–20 (30 tablets, 50 mg) |
18. FAQs (15 Questions)
- What is azathioprine used for?
Azathioprine is used to prevent organ rejection and treat autoimmune diseases like rheumatoid arthritis and Crohn’s disease. - How does azathioprine work?
It suppresses the immune system by inhibiting purine synthesis, reducing immune cell activity. - Can azathioprine be taken with food?
Yes, it is best taken with food to minimise nausea. - What are the common side effects of azathioprine?
Nausea, vomiting, and appetite loss. - Are there any serious side effects?
Bone marrow suppression, increased infection risk, and malignancy are serious risks. - Can pregnant women take azathioprine?
It is not recommended unless necessary, due to foetal risks. - Can children use azathioprine?
Yes, particularly in paediatric transplant patients. - How should azathioprine be stored?
Store at room temperature, away from light and moisture. - What happens if I miss a dose?
Take it as soon as you remember, but skip it if it’s near the next dose. Do not double the dose. - Can azathioprine interact with other medications?
Yes, it interacts with allopurinol, ACE inhibitors, and warfarin. - Does azathioprine increase infection risk?
Yes, it suppresses the immune system, making infections more likely. - Is azathioprine safe for elderly patients?
Yes, but with careful monitoring for infections and organ function. - What tests are required while on azathioprine?
Regular blood tests for CBC, liver function, and renal function. - Can azathioprine cause cancer?
Yes, there is an increased risk of lymphoma and skin cancer. - Do I need to avoid vaccines while on azathioprine?
Live vaccines should be avoided during treatment.