A from the upper small intestine is a zero-or- der process and is strongly influenced by bile secretion, pancreatic exocrine secretion, food

der process and is strongly influenced by bile secretion, pancreatic exocrine secretion, food intake and gastrointestinal motility4. For this reason, many formulations have been proposed to improve the gastrointestinal absorption of cyclosporine A. In 1996, a cyclosporine A formulation in a microemulsion concentrate, containing a surfactant, lipophilic and hydrophilic solvents and an organic solvent had been introduced in therapy5. The microemulsion is characterised by a droplet size < 100 nm and is absorbed, independently from other exogenous or endogenous factors, in a dose-related manner6-8. Very recently, a new cyclosporine A microemulsion, characterised by a high uniformity of droplet size (32 ± 1 nm) has been developed by Sigma Pharma (Brazil)9. The aim of our study was to investigate in healthy volunteers the pharmacokinetics of this new cyclosporine A microemulsion formulation comparing its bioavailability with the standard market microemulsion formulation.