Improvement of peroral absorption of cyclosporine A by microemulsions.

The rat was found to be a suitable model for pharmacokinetic and bioavailability studies of cyclosporine A (CsA). All pharmacokinetic parameters studied were in the same order of magnitude as those found in man. Two peroral formulations in the form of microemulsions were compared with a commercially available P.O. solution (to be diluted for administration) and a solution for intravenous administration. Of the two microemulsions, one resulted in an extent of absolute and relative bioavailability significantly higher than that of the available P.O. solution. Biliary recycling was observed upon all routes of administration. If uncorrected for biliary recycling, both absolute and relative bioavailability are overestimated.