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Pharmacologic class: Purine antagonist
Therapeutic class: Immunosuppressant
Pregnancy risk category D
FDA Box Warning
• Drug may cause chronic immunosuppression, increasing neoplasia risk. Physicians using it should be familiar with this risk and with possible hematologic toxicities and mutagenic potential in both sexes.
Prevents proliferation and differentiation of activated B and T cells by interfering with synthesis of purine, DNA, and RNA
Injection: 100-mg vial
Tablets: 50 mg, 75 mg, 100 mg
Indications and dosages
➣ To prevent rejection of kidney transplant
Adults and children: Initially, 3 to 5 mg/kg/day P.O. or I.V. as a single dose. Give on day of transplantation or 1 to 3 days before day of transplantation; then 3 to 5 mg/kg/day I.V. after surgery until patient can tolerate P.O. route. Maintenance dosage is 1 to 3 mg/kg/day P.O.
➣ Rheumatoid arthritis
Adults and children: Initially, 1 mg/kg P.O. or I.V. in one or two daily doses. Increase dosage in steps at 6 to 8 weeks and thereafter at 4-week intervals; use dosage increments of 0.5 mg/kg/day, to a maximum dosage of 2.5 mg/kg/day. Once patient stabilizes, decrease in decrements of 0.5 mg/kg/day to lowest effective dosage.
• Renal disease
• Concurrent allopurinol therapy
• Elderly patients
• Crohn's disease
• Myasthenia gravis
• Chronic ulcerative colitis
• Hypersensitivity to drug
• Pregnancy or breastfeeding
Use cautiously in:
• chickenpox, herpes zoster, impaired hepatic or renal function, decreased bone marrow reserve
• previous therapy with alkylating agents (cyclophosphamide, chlorambucil, melphalan) for rheumatoid arthritis
• elderly patients
• women of childbearing age.
• Give after meals.
• Be aware that I.V. administration is intended for use only when patients can't tolerate oral medications.
GI: nausea, vomiting, diarrhea, stomatitis, esophagitis, anorexia, mucositis, pancreatitis
Hematologic: anemia, thrombocytopenia, leukopenia, pancytopenia
Hepatic: jaundice, hepatotoxicity
Musculoskeletal: muscle wasting, joint and muscle pain
Skin: rash, alopecia
Other: chills, fever, serum sickness, neoplasms, serious infection
Drug-drug. Allopurinol: increased therapeutic and adverse effects of azathioprine
Angiotensin-converting enzyme (ACE) inhibitors, co-trimoxazole: severe leukopenia
Anticoagulants, cyclosporine: decreased actions of these drugs
Atracurium, pancuronium, tubocurarine, vecuronium: reversal of these drugs' actions
Drugs affecting bone marrow and bone marrow cells (such as ACE inhibitors, co-trimoxazole): severe leukopenia
Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, amylase, aspartate aminotransferase, bilirubin: increased levels
Albumin, hemoglobin, uric acid: decreased levels
Urine uric acid: decreased level
Drug-herbs. Astragalus, echinacea, melatonin: interference with immunosuppressant action
☞ Monitor CBC, platelet level, and liver function test results.
• Assess for signs and symptoms of hepatotoxicity (clay-colored stools, pruritus, jaundice, and dark urine).
• Watch for signs and symptoms of infection.
• Monitor for bleeding tendency and hemorrhage.
☞ Tell patient that drug lowers resistance to infection. Instruct him to immediately report fever, cough, breathing problems, chills, and other symptoms.
☞ Instruct patient to immediately report unusual bleeding or bruising.
• Tell patient that drug effects may not be obvious for up to 8 weeks in immunosuppression and up to 12 weeks for rheumatoid arthritis relief.
☞ Emphasize importance of avoiding pregnancy during therapy and for 4 months afterward.
• Caution patient to avoid activities that may cause injury. Tell him to use soft toothbrush and electric razor to avoid gum and skin injury.
• Advise patient to minimize GI upset by eating small, frequent servings of food and drinking plenty of fluids.
• Tell patient he'll undergo regular blood testing during therapy.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and herbs mentioned above.
azathioprineA thiolated purine analogue/immunosuppressant used to prevent rejection of heart, kidney, lung and other allografts, acting primarily on T cells; it is used in rheumatoid arthritis and myasthenia gravis.
Dose-related marrow suppression—leukopaenia, thrombocytopaenia, macrocytic anaemia); GI tract—nausea, vomiting, diarrhoea, fever, malaise, myalgia, liver enzyme defects, hepatotoxicity, pancreatitis. Azathiprineshould not be given with allopurinol.
Azathioprine is 6-mercaptopurine with a side chain to protect the labile sulfhydryl group, which is split off in the liver; full metabolic activity follows addition of ribose 5-phosphate from phosphoribosyl pyrophosphate that is metabolised to the cytotoxic derivative 6-mercaptopurine.