Azathioprine

Administration

  • Type: immunosuppressant
  • Dosage Forms: tablet, powder for injection (IV form unavailable in US)
  • Dosage Strengths: tablet: 50, 75, 100mg; powder for injection: 100mg/vial
  • Routes of Administration: PO, IV (unavailable in US)
  • Common Trade Names: Azasan, Imuran

Adult Dosing

Kidney transplant rejection prophylaxis

  • 1-3mg/kg PO QD
  • Start: 3-5mg/kg PO x1 up to 3 days before transplant; Info: transplant protocols may vary

Rheumatoid arthritis, severe

  • 1-2.5mg/kg/day PO divided QD-bid
  • Start: 1mg/kg/day PO divided QD-bid; Max: 2.5mg/kg/day; Info: after 6-8wk may increase 0.5mg/kg/day q4wk

Crohns Disease

  • 100-250mg PO QD
  • Start: 50mg PO QD; Max: 2.5mg/kg/day; Info: for induction or remission maintenance and fistulizing disease, steroid-sparing effects

Ulcerative colitis

  • 100-250mg PO QD
  • Start: 50mg PO QD; Max: 2.5mg/kg/day; Info: for induction or remission maintenance, steroid-sparing effects

Pediatric Dosing

Kidney transplant rejection prophylaxis

  • 1-3mg/kg PO QD
  • Start: 3-5mg/kg PO x1 up to 3 days before transplant; Info: transplant protocols may vary

Juvenile idiopathic arthritis, severe

  • 1-2.5mg/kg/day PO divided QD-bid
  • Start: 1mg/kg/day PO divided QD-bid; Max: 2.5mg/kg/day; Info: after 6-8wk may increase 0.5mg/kg/day q4wk

Special Populations

Renal Dosing

  • Adult: CrCl 10-50: decrease dose 25%; CrCl <10: decrease dose 50%; HD: give 0.25mg/kg supplement; PD: not defined
  • Pediatric: CrCl 10-50: decrease dose 25% or give q36h; CrCl <10: decrease dose 50% or give q48h; HD: give supplement; PD: not defined

Hepatic Dosing

  • Adult: not defined; caution advised
  • Pediatric: not defined; caution advised

Contraindications

  • Allergy to class/drug
  • pregnancy (RA use)
  • caution if renal impairment
  • caution if prior alkylating agents

Adverse Reactions

Serious

  • leukopenia
  • thrombocytopenia
  • anemia
  • myelosuppression
  • immunosuppression
  • infection
  • PML
  • GI hypersensitivity reaction
  • pancreatitis
  • hepatotoxicity
  • hepatic veno-occlusive disease
  • lymphoma
  • malignancy
  • acute febrile neutrophilic dermatosis

Common

  • leukopenia
  • thrombocytopenia
  • anemia
  • infection
  • nausea
  • vomiting
  • anorexia
  • diarrhea
  • ALT, AST elevated
  • malaise
  • myalgia
  • fever
  • rash
  • malignancy

Pharmacology

  • Half-life: 5 hours
  • Metabolism: liver extensively, erythrocytes; CYP450
  • Excretion: bile, urine (1-2% unchanged)

Mechanism of Action

Acts as a prodrug for mercaptopurine, inhibiting an enzyme required for the synthesis of DNA. Thus, it most strongly affects proliferating cells, such as the T cells and B cells of the immune system

Comments

See Also

References

epocrates