AZATHIOPRINE
Imuran, Azasan


DOSING: ADULTS 

 Initial: 50 mg daily; may increase by 25 mg/day every 1-2 weeks as tolerated to target dose of 2-3 mg/kg/day


DOSING IN RENAL IMPAIRMENT

Decrease by 50%


DOSAGE FORMS 

Tablet [scored]: 50 mg
Azasan: 75 mg, 100 mg
Imuran: 50 mg


SIGNIFICANT ADVERSE REACTIONS 

Alopecia
Rash
Diarrhea
Pancreatitis
Leukopenia- Patients with genetic deficiency of thiopurine  methyltransferase (TPMT) may be sensitive to myelosuppressive  effects. Patients on concurrent therapy with drugs which may inhibit TPMT (eg, olsalazine) or xanthine oxidase (eg, allopurinol) may be sensitive to myelosuppressive effects.
Macrocytic anemia
Hepatotoxicity
Infection secondary to immunosuppression
Malignancy


CONTRAINDICATIONS 
 Hypersensitivity to azathioprine or any component of the formulation; pregnancy


DRUG INTERACTIONS

ACE inhibitors: Concomitant therapy may induce anemia and severe leukopenia.
Allopurinol: May increase serum levels of azathioprine's active metabolite (mercaptopurine). Decrease azathioprine dose to ~25% of the normal dose; monitor for toxic effects of azathioprine.
Aminosalicylates (olsalazine, mesalamine, sulfasalazine): May inhibit TPMT, increasing toxicity/myelosuppression of azathioprine.
Mercaptopurine: Azathioprine is metabolized to mercaptopurine; concomitant use may result in profound myelosuppression and should be avoided.
Warfarin: Effect may be decreased by azathioprine.


PREGNANCY RISK FACTOR  D.  Azathioprine crosses the placenta in humans; congenital anomalies, immunosuppression, and intrauterine growth retardation have been reported. There are no adequate and well-controlled studies in pregnant women.


LACTATION — Enters breast milk/not recommended.