Clinical pharmacokinetics of ciclosporin A in bone marrow transplantation patients.

Ciclosporin A (CsA) plasma concentrations were monitored by radioimmunoassay after administration IV and PO to 15 patients before allogeneic bone marrow transplantation. The clearance (10.4 +/- 5.41 1/h), half-life (26.4 +/- 14.6 h), and bioavailability (16% +/- 10%) calculated directly from experimental data showed wide interindividual variations. The kinetics after IV infusion, monitored over 2-5 days, appeared to be triphasic. A three-compartment open mamillary model was thus used to simulate the distribution and elimination kinetics of CsA. The distributive delay between administration PO and absorption in the plasma was approximated using a series of six additional compartments connected with a single transfer rate constant. Then, for each patient, the experimental data corresponding to both IV and PO administration were fitted using a single set of rate constants. Clearance and bioavailability calculated from model parameters correlated well with direct estimations obtained from the areas under the concentration time curves. Drug monitoring and linear modeling will be used in an attempt to achieve stable predetermined plasma concentrations of CsA in bone marrow transplantation patients receiving the drug either IV or PO.