Effect of hematocrit on cyclosporine (cyclosporin A) in whole blood and plasma of renal-transplant patients.

Cyclosporine concentrations in whole blood and plasma were determined in 25 samples from renal-transplant patients. The portion of cyclosporine carried in plasma varied widely, from 9 to 58%. Radioimmunoassay and liquid chromatography both revealed a statistically significant inverse correlation between hematocrit and the plasma fraction of cyclosporine in the circulating blood. Regression analysis indicates that a 10% increase in hematocrit would decrease the portion of cyclosporine in plasma by 12 to 14%. Studies with cyclosporine-supplemented samples further demonstrated an effect of hematocrit on the drug concentration in plasma without a corresponding effect on the concentration in whole blood. The distribution of cyclosporine between plasma and erythrocytes was unaffected by plasma cholesterol and triglycerides for these transplant patients.