Objective: To assess whether patients with rheumatoid arthritis (RA) may be converted, on a milligram-to-milligram basis, from conventional cyclosporin A (CyA, Sandimmun) to the microemulsion formulation (Neoral) with maintenance of longterm safety, and to compare cyclosporin A (CyA) pharmacokinetics between formulations.
Methods: In this double blind, multicenter, parallel group study, 51 patients receiving stable conventional CyA maintenance treatment were randomized to continue conventional CyA (n = 27) or to convert to CyA microemulsion (n = 24) and were monitored for 52 weeks. Trough blood CyA levels were measured before and at intervals after conversion. CyA steady-state area under the curve was assessed one week before and 2 and 6 weeks after randomization in 15 patients in each treatment arm. CyA trough levels and pharmacokinetic results remained unknown to investigators throughout the study. CyA doses were titrated as necessary on the basis of clinical evaluation and disease activity assessments.
Results: Initial mean daily doses were 3.5 mg/kg/day (conventional CyA) and 3.3 mg/kg/day (CyA microemulsion) and did not change significantly during the study. The mean bioavailability of CyA from the microemulsion formulation was 23% higher than from conventional CyA. Replicate assessments indicated a more reproducible pharmacokinetic profile with CyA microemulsion. The overall incidence and nature of adverse events and changes in vital signs and laboratory variables were similar in both groups. No clinically relevant differences in efficacy were found between treatments. No loss of efficacy and no tolerability problems occurred after conversion from conventional to microemulsion CyA.
Conclusion: Existing CyA dosing guidelines, formulated for conventional CyA, are suitable for longterm CyA microemulsion therapy of patients with RA. These results indicate the pharmacokinetic advantages of the microemulsion formulation.