AZATHIOPRINE

AZATHIOPRINE
(ay-za-thye'oh-preen)
Azasan, Imuran
Classifications: immunosuppressant; antiinflammatory; disease-modifiying rheumatic drug (dmard);
Therapeutic:immunosuppressant
; antiinflammatory; antirheumatic; dmard
Prototype: Cyclosporine
Pregnancy Category: D

Availability

25 mg, 50 mg, 75 mg, 100 mg tablets; 100 mg vial

Action

Antagonizes purine metabolism and appears to inhibit DNA, RNA, and normal protein synthesis in rapidly growing cells.

Therapeutic Effect

Suppresses T cell effects before transplant rejection. Has immunosuppressant and antiinflammatory properties.

Uses

Adjunctive agent to prevent rejection of kidney allografts, usually with other immunosuppressants. Also used in selective adult patients with severe, active rheumatoid arthritis; unresponsive to conventional therapy.

Unlabeled Uses

SLE, lupus nephritis, psoriatic arthritis; ulcerative colitis, pemphigus, nephrotic syndrome, and other inflammatory and immunologic diseases.

Contraindications

Hypersensitivity to azathioprine or mercaptopurine; clinically active infection, immunization of patient or close family members with live virus vaccines; anuria; pancreatitis; patients receiving alkylating agents (increased risk of neoplasms), concurrent radiation therapy; pregnancy (category D), lactation.

Cautious Use

Impaired kidney and liver function; patients receiving cadaver kidney; myasthenia gravis.

Route & Dosage

Renal Transplantation
Adult: PO 3–5 mg/kg/d initially, may be able to reduce to 1–3 mg/kg/d IV 3–5 mg/kg/d initially, may be able to reduce to 1–3 mg/kg/d; transfer to PO

Rheumatoid Arthritis
Adult: PO 1 mg/kg/d initially, may be increased by 0.5 mg/kg/d at 4–6 wk intervals if needed up to 2.5 mg/kg/d

Obesity
Doses calculated on IBW.

Renal Impairment
Clcr 10–50 mL/min: 75% of usual dose; <10 mL/min: 50% of usual dose
Hemodialysis: Administer after dialysis

Administration

Oral
  • Give oral drug in divided doses (as prescribed) with food or immediately after meals to minimize gastric disturbances.
Intravenous

PREPARE: Direct/Intermittent: Reconstitute by adding 10 mL sterile water for injection into vial; swirl until dissolved. May be given as prepared or further diluted with 50 mL NS, D5W, or D5/NS. Reconstituted solution may be stored at room temperature but must be used within 24 h after reconstitution (contains no preservatives).  

ADMINISTER: Direct/Intermittent: May infuse over 30 min to 8 h. Typical infusion time is 30–60 min or longer. If longer infusion time is ordered, the final volume of the IV solution is increased appropriately. Check with physician.  

  • Store at 15°–30° C (59°–86° F) in tightly closed, light-resistant containers unless otherwise directed.

Adverse Effects (≥1%)

Body as a Whole: Hypersensitivity (skin eruptions, rash, arthralgia). GI: Nausea, vomiting, anorexia, esophagitis, diarrhea, steatorrhea, hepatitis with elevations in bilirubin, alkaline phosphatase, AST, ALT, biliary stasis, toxic hepatitis. Hematologic: Bone marrow depression, thrombocytopenia, leukopenia, anemia, agranulocytosis, pancytopenia. Other: Secondary infection (immunosuppression); dysarthria, alopecia; carcinogenic and teratogenic potential reported.

Diagnostic Test Interference

Azathioprine may decrease plasma and urinary uric acid in patients with gout.

Interactions

Drug: Allopurinol increases effects and toxicity of azathioprine by reducing metabolism of the active metabolite; allopurinol doses should be decreased by one third or one fourth; tubocurarine and other nondepolarizing skeletal muscle relaxants may reverse or inhibit neuromuscular blocking effects.

Pharmacokinetics

Absorption: Readily from GI tract. Distribution: Crosses placenta. Metabolism: Extensively in liver to active metabolite mercaptopurine. Elimination: In urine. Half-Life: 3 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor therapeutic effectiveness which usually requires 6–8 wk of therapy for patients with rheumatoid arthritis (improvement in morning stiffness and grip strength). If no improvement has occurred after 12-wk trial period, drug is generally discontinued.
  • Lab tests: Perform CBC, including Hgb and platelet counts, prior to and at least weekly during first month of therapy, twice monthly during second and third months, and monthly, or more frequently thereafter, if indicated (e.g., by dosage or therapy changes).
  • Monitor for toxicity. Drug has a high toxic potential. Because it may have delayed action, dosage should be reduced or drug withdrawn at the first indication of an abnormally large or persistent decrease in leukocyte or platelet count to avoid irreversible bone marrow depression.
  • Monitor vital signs. Report signs of infection.
  • Monitor kidney function (urine protein, urine electrolytes, creatinine clearance, serum creatinine, BUN) periodically.
  • Monitor I&O ratio; note color, character, and specific gravity of urine. Report an abrupt decrease in urinary output or any change in I&O ratio.
  • Monitor liver function (alkaline phosphatase, AST, ALT, serum bilirubin) and repeat at least every 3 mo or more frequently if indicated. If hepatic toxicity (see Appendix F) develops, therapy may have to be withdrawn.
  • Monitor for signs of abnormal bleeding [easy bruising, bleeding gums, petechiae, purpura, melena, epistaxis, dark urine (hematuria), hemoptysis, hematemesis]. If thrombocytopenia occurs, invasive procedures should be withheld, if possible.
  • Use protective isolation for the hospitalized patient to reduce risk of infections.

Patient & Family Education

  • Avoid contact with anyone who has a cold or other infection and report signs of impending infection. Exercise scrupulous personal hygiene because infection is a constant hazard of immunosuppressive therapy.
  • Practice birth control during therapy and for 4 mo after drug is discontinued. This drug is associated with potential hazards in pregnancy.
  • Do not receive/take vaccinations or other immunity-conferring agents during therapy because they may precipitate unusually severe reactions due to the immunosuppressive effects of the drug.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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