Equilibrium Dialysis in a Stainless Steel Chamber, Measurement of the Free Plasma Fraction of Cyclosporin

The aim of this study was to demonstrate the sealing of a prototype stainless steel dialysis chamber and the reproducibility of the results after using the chamber to measure the free plasma fraction of cyclosporin. The chamber comprised two compartments (A and B), in each of which was a hemisphere of approximately 1-mL capacity. To demonstrate sealing, equilibrium dialysis was carried out simultaneously in 10 chambers, but in which the semipermeable membrane separating the two compartments was substituted by an impermeable membrane. Chamber sealing was checked by the absence of liquid in the compartment B at the end of dialysis. To test reproducibility, equilibrium dialysis was carried out in 10 chambers containing cyclosporin. The mean value for the free plasma fraction of cyclosporin was 0.65%, giving a coefficient of variation within the acceptable limit of error. The use of this stainless steel chamber is recommended when large numbers of dialyses of cyclosporin must be carried out frequently.