Safe conversion of mycophenolate mofetil to azathioprine in kidney transplant recipients with sirolimus-based immunosuppression

Aim: Mycophenolate mofetil (MMF) is a powerful immunosuppressive drug with established efficacy and safety. The long-term use of MMF may bring increased risk of for infection and malignancy and also increased cost of transplantation. The search for minimization of immunosuppressive protocol has led to an open randomized clinical trial of conversion from MMF to azathioprine (AZA). Methods: A total of 50 kidney allograft recipients treated with prednisone, sirolimus and MMF were randomized into two groups: converted (AZA group) and continuing (MMF group). The average duration of MMF therapy prior to conversion was 43 months in each group. Inclusion criteria included: patients with serum creatinine levels of less than 200 mu mol/L; no past history of acute vascular rejection or recent acute rejection 6 months before randomization; and normal liver function tests. Results: Baseline demographics were similar in the two groups. During the 12 month observation period, there were no acute rejection episodes in either group. There were no significant differences in overall patient or graft survival or function. AZA-treated patients had a lower incidence of gastrointestinal complications (P = 0.03). Daily cost reduction in the AZA group was more than $US8.79/day per patient. Conclusion: In general, replacing MMF with AZA in stable renal transplant recipients is well tolerated and was cost effective with no increased risk of rejection. As the this study was on relatively small samples, larger and longer follow-up studies will be needed to confirm these expected advantages for the long-term outcome and to assess the long-term safety of this minimization of immunosuppressive therapy.