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Uses

Renal Allotransplantation

Prevention of rejection of renal allografts.

Rheumatoid Arthritis

Management of the signs and symptoms of rheumatoid arthritis.

Crohn’s Disease

Has been used to induce and maintain remission in adults with moderate to severely or chronically active Crohn’s disease†.

Has been used in the management of fistulizing Crohn’s disease†.

Has been used in children with refractory or corticosteroid-dependent Crohn’s disease†.

Dosage and Administration

General

• Azathioprine is an antimetabolite and is handled according to guidelines for cytotoxic drugs. Consult specialized references for procedures for proper handling and disposal of hazardous drugs.

Administration

Administer orally or by slow IV injection or IV infusion.

Low-dose corticosteroids and NSAIAs (including aspirin) may be continued in patients with rheumatoid arthritis. The manufacturers state that combined use of azathioprine and other disease modifying antirheumatic drugs (DMARDs) has not been studied and is not recommended.

Oral Administration

Administer once or twice daily.

IV Administration

When used for renal allotransplantation, the IV route may be used initially in patients unable to tolerate oral medication. Institute oral therapy as soon as possible (at the same dosage).

Reconstitution and Dilution

For solution and drug compatibility information, see Compatibility under Stability.

Reconstitute vial containing 100 mg of azathioprine with 10 mL of sterile water for injection. Reconstituted solution may be further diluted prior to administration (final volume depends on infusion time).

Rate of Administration

Usually infused over 30–60 minutes; may be administered over 5 minutes to 8 hours.

Dosage

Available as azathioprine and azathioprine sodium; dosage expressed as azathioprine.

Consider determining thiopurine methyl transferase (TPMT) phenotype or genotype prior to initiation of therapy and using results to select dosage. (See Hematologic Effects and TPMT Testing under Cautions.)

If rapid fall in leukocyte count, persistent leukopenia, or other evidence of bone marrow suppression develops, temporarily discontinue or reduce dosage. Consider TPMT testing in patients with abnormal CBC results that persist despite dosage reduction. (See Hematologic Effects and TPMT Testing under Cautions.)

If used with allopurinol, adjustment in the treatment regimen recommended. (See Specific Drugs under Interactions.)

If severe, continuous rejection occurs, it is probably preferable to allow the allograft to be rejected than to increase the dosage of azathioprine to very toxic levels.

Pediatric Patients

Renal Allotransplantation

Oral

Initially, 3–5 mg/kg as a single daily dose has been used beginning on the day of transplantation (and in some cases 1–3 days before transplantation). Reduction to maintenance dosage of 1–3 mg/kg daily usually possible.

IV

3–5 mg/kg as a single daily dose has been used beginning on the day of transplantation (and in some cases 1–3 days before transplantation) until the patient is able to tolerate oral administration (usually 1–4 days).

Crohn’s Disease

Oral

1.5–2 mg/kg daily has been used.†

Adults

Renal Allotransplantation

Oral

Initially, 3–5 mg/kg as a single daily dose beginning on the day of transplantation (and in some cases 1–3 days before transplantation). Reduction to maintenance dosage of 1–3 mg/kg daily usually possible.

IV

3–5 mg/kg as a single daily dose beginning on the day of transplantation (and in some cases 1–3 days before transplantation) until the patient is able to tolerate oral administration (usually 1–4 days).

Rheumatoid Arthritis

Oral

Initially, 1 mg/kg (50–100 mg) daily in 1 or 2 doses.

If initial response unsatisfactory and there are no serious adverse effects after 6–8 weeks, the daily dosage may be increased by 0.5 mg/kg. Thereafter, daily dosage may be increased, if needed, by 0.5 mg/kg every 4 weeks up to a maximum dosage of 2.5 mg/kg daily. Patients whose disease does not improve after 12 weeks of therapy are considered nonresponders.

When used for maintenance dosage, use lowest effective dosage to reduce toxicities. Dosage can be reduced in increments of 0.5 mg/kg (approximately 25 mg) daily every 4 weeks while other therapy is kept constant.

Optimum duration of therapy undetermined.

Crohn’s Disease

Oral

2–4 mg/kg daily has been used.†

Prescribing Limits

Adults

Rheumatoid Arthritis

Oral

Maximum 2.5 mg/kg daily.

Special Populations

Dosage in Renal Impairment

Use low initial dosage in patients with renal impairment.

Renal Allotransplantation

Lower dosage may be necessary in relatively oliguric patients, especially in those with tubular necrosis in the immediate posttransplant period.