RESUMEN
BACKGROUND: The use of conventional cyclosporine (Sandimmune) requires great care, as this drug exhibits a narrow therapeutic index and wide interindividual variability in its pharmacokinetics. Recently, a new microemulsion formulation (Neoral) was developed. With this formulation, cyclosporine is absorbed at the small intestine without the presence of bile. Therefore, the objective of this study was to compare the bioavailability of cyclosporine after the administration of conventional and microemulsion formulations in healthy Mexican volunteers in order to approach the optimal dosage regimen of microemulsion in the Mexican population. METHODS: The trial was conducted using 23 healthy volunteers according to a randomized crossover design. Volunteers received one 7.5-mg/kg dose as each formulation, with a 1-week washout period between treatments. Blood samples of 0.5 mL were obtained according to the following schedule: 0, 0.5, 1, 2, 3, 4, 5, 6, 8, 12, and 24 h after medication. RESULTS: These indicated that Cmax and AUC0-24 values were higher with the microemulsion than with the conventional formulation. CONCLUSIONS: The microemulsion had a better absorption profile than the conventional formulation, because plasma levels with the conventional formulation demonstrated oscillations rather than reflecting an erratic absorption. Lower doses of the microemulsion are required to obtain Cmax values similar to those obtained with conventional cyclosporine.