LONG-TERM RESULTS OF MIZORIBINE-TREATED RENAL TRANSPLANT RECIPIENTS-----A PROSPECTIVE, RANDOMIZED TRIAL OF MIZORIBINE AND AZATHIOPRINE UNDER CYCLOSPORINE-BASED IMMUNOSUPPRESSION.

238 INTRODUCTION AND OBJECTIVES: Mizoribine (MZ) is known to have a stronger immunosuppressive effect than azathioprine (AZ), and less myelosuppressive and hepatotoxic effects. However, no randomized trial of MZ in renal transplantation has been reported so far. Therefore, we designed this prospective, randomized study to evaluate the immunosuppressive effect of MZ in renal transplantation. MATERIALS AND METHODS: Between January, 1988 and April, 1989, 116 patients were entered into a randomized trial comparing MZ and AZ under cyclosporine (CyA)-based immunosuppression. Both groups (MZ group and AZ group) consisted of 58 patients. There was no significant difference between the two groups in the patient background. In the induction phase, methylprednisolone (MP), CyA, and MZ or AZ were used. AZ administration, 1-2 mg/kg per day, was started 2 days before transplantation, and adjusted according to the peripheral white blood cell count. MZ administration, 4-5 mg/kg per day, was started 2 days before transplantation, and continued the same dosage unless an adverse effect, such as myelosuppression occurred, in which it was discontinued. RESULTS: Overall 1-, 5-, and 9-year patient survival was 98%, 94%, and 85%, respectively; in the MZ group it was 98%, 93%, and 88%, respectively, and in the AZ group, 97%, 95%, and 83%, respectively. Overall 1-, 5-, and 9-year graft survival was 92%, 75%, and 55%, respectively; in the MZ group it was 90%, 73%, and 58%, respectively, and in the AZ group, 93%, 73%, and 52%, respectively. There was no significant difference between the two groups in terms of the graft and patient survival. The incidence of acute rejection was 56.9% in both groups. Sixteen AZ group patients were forced to discontinue AZ administration or change from AZ to MZ due to adverse effects, which were myelosuppression in 11 patients, and liver dysfunction in 5 patients. Since no MZ-related adverse effect occurred, no patient discontinued MZ in the MZ group. CONCLUSIONS: Although there was no significant difference in terms of patient and graft survival, and the incidence of rejection episodes, MZ showed much less adverse effects than AZ. Therefore, MZ seems to be a much more useful immunosuppressive agent for renal transplantation than AZ.