Drug information of Azathioprine

Azathioprine


Azathioprine lowers your body's immune system. The immune system helps your body fight infections. The immune system can also fight or "reject" a transplanted organ such as a liver or kidney. This is because the immune system treats the new organ as an invader. Azathioprine is used to prevent your body from rejecting a transplanted kidney. It is also used to treat symptoms of rheumatoid arthritis.

Mechanism of effect

Azathioprine antagonizes purine metabolism and may inhibit synthesis of DNA, RNA, and proteins. It may also interfere with cellular metabolism and inhibit mitosis. Its mechanism of action is likely due to incorporation of thiopurine analogues into the DNA structure, causing chain termination and cytotoxicity.

Pharmacodynamic

Azathioprine is a chemotherapy drug, now rarely used for chemotherapy but more for immunosuppression in organ transplantation and autoimmune disease such as rheumatoid arthritis or inflammatory bowel disease or Crohn's disease.

Pharmacokinetics

Azathioprine is well absorbed following oral administration. Maximum serum radioactivity occurs at 1 to 2 hours after oral 35S-Azathioprine and decays with a half-life of 5 hours. Azathioprine and the metabolite mercaptopurine are moderately bound to serum proteins (30%).Azathioprine is metabolized to 6-mercaptopurine (6-MP). Both compounds are rapidly eliminated from blood and are oxidized or methylated in erythrocytes and liver; no Azathioprine or mercaptopurine is detectable in urine after 8 hours.

Dosage

Usual Adult Dose for Renal Transplant Initial dose: 3 to 5 mg/kg orally or IV once a day, beginning at the time of transplant Maintenance dose: 1 to 3 mg/kg orally or IV once a day Usual Adult Dose for Rheumatoid Arthritis Initial dose: 1 mg/kg (50 to 100 mg) orally or IV per day given in 1 to 2 divided doses Maintenance dose: Lowest effective dose Maximum dose: 2.5 mg/kg orally or IV per day Duration: At least 12 weeks Usual Pediatric Dose for Organ Transplant - Rejection Prophylaxis Initial dose: 3 to 5 mg/kg orally or IV once a day, beginning at the time of transplant Maintenance dose: 1 to 3 mg/kg orally or IV once a day

Alerts

1-Patients receiving immunosuppressants, including Azathioprine, are at increased risk of developing lymphoma and other malignancies, particularly of the skin. 2-Severe leukopenia, thrombocytopenia, anemias including macrocytic anemia, and/or pancytopenia may occur in patients being treated with Azathioprine. Severe bone marrow suppression may also occur. 3-Patients receiving immunosuppressants, including Azathioprine, are at increased risk for bacterial, viral, fungal, protozoal, and opportunistic infections, including reactivation of latent infections. These infections may lead to serious, including fatal outcomes. 4-A gastrointestinal hypersensitivity reaction characterized by severe nausea and vomiting has been reported. Symptoms of gastrointestinal toxicity most often develop within the first several weeks of therapy with Azathioprine and are reversible upon discontinuation of the drug.

Points of recommendation

1-Patients being started on Azathioprine should be informed of the necessity of periodic blood counts while they are receiving the drug and should be encouraged to report any unusual bleeding or bruising to their physician. 2-Careful dosage instructions should be given to the patient, especially when Azathioprine is being administered in the presence of impaired renal function or concomitantly with allopurinol.

Pregnancy level

D


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