A survey to determine the blood concentration of cyclosporine 2 hours postdose in stable renal transplant patients.

The current method for monitoring cyclosporine measures predose concentrations (C0). A better method has been developed, namely, measurement of the blood cyclosporine concentration at 2 hours postdose (C2). The aim of this survey was to determine the variability of C0 and C2 concentrations among stable renal transplant patients. One hundred two stable renal transplant patients who were at least 6 months posttransplant were recruited from the renal transplant outpatient clinic. The cyclosporine dose was between 100 and 500 mg daily; all patients had been monitored using C0 concentrations. Blood samples for cyclosporine concentration measurements were taken at both C0 and C2 at two consecutive clinic visits. The within- and between-patient variabilities were calculated using nested analysis of variance. The mean age was 50 years (21 to 81); the mean weight was 75 kg. The mean cyclosporine dose was 3.18 mg/kg/d (1.2 to 8.8). The average serum creatinine was 174 micromol/L (77 to 626) and the average cholesterol was 5 micromol/L (3 to 9). The mean (+/-SD) C0 concentration was 150 (47.31) microg/L and C2=895 (239) microg/L. The C0 concentration varied over 16-fold between patients compared to a sevenfold variation in C2. The between-subject coefficient of variation (CV) was 35% for C0 and 30% for C2 and the within subject CV was 23% for C0 and 20% for C2. The results suggest that cyclosporine concentrations at C0 are slightly more variable than those at C2. Whether this modest reduction in variability results in better patient outcomes is the subject of the next phase of this study.