Background: There are conflicting reports in the literature concerning the efficacy of maintenance immunosuppression in renal transplantation with a regimen of azathioprine and steroids.
Methods: The daily dosage (mg/kg) of azathioprine administered 1 year after transplantation was analyzed in relation to subsequent long-term graft outcome. Transplants performed from 1985 to 1996 and reported to the Collaborative Transplant Study were analyzed.
Results: In patients on maintenance immunosuppression without cyclosporine, the daily dosage of azathioprine had a highly significant influence on long-term graft outcome. Patients who received > 1.5 mg/kg/ day of azathioprine had a 69% graft survival rate at 7 years, compared with a 55% rate in patients receiving 1.01-1.5 mg/kg/day (P<0.0001) and a 45% rate in patients receiving < or = 1.00 mg/kg/day (P<0.0001). This observation was valid for patients who were taken off cyclosporine during the first year as well as for patients who were treated with azathioprine and steroids (without cyclosporine) from the beginning.
Conclusion: Maintenance immunosuppression with azathioprine and steroids results in good long-term kidney graft survival, provided azathioprine is administered at a daily dose of >1.5 mg/kg.