INFLUENCE OF 2 COMMERCIAL FIBERS IN THE PHARMACOKINETICS OF ETHINYLESTRADIOL IN RABBITS

Fiber formulations are used in human nutrition owing to their benefici al properties for health. It is probable that ingestion of fiber coinc ides with the oral administration of drugs, and a modification of its oral absorption, and therefore of its pharmacokinetics, can appear. In the present study, the compartmental and noncompartmental pharmacokin etic parameters of ethinylestradiol (EE) in rabbits after oral adminis tration were determined. It was also studied whether the presence of t wo different fiber formulations [A, wheat bran (76.5%), fruit fiber (1 2%) and guar gum (2%) and B, Plantago ovata seeds (65%) and P. ovata s eed cuticles (2.2%)] in the gastrointestinal tract modified the pharma cokinetics of EE when administered at the same time. Three groups of r abbits were used: control, fiber A and fiber B. The animals in all thr ee groups received 1 mg/kg b. wt. EE. The estrogen was administered al one in the control group and in the presence of 4 g of fiber A and fib er B, respectively, in the other two groups. After compartmental (two- compartment open model) and noncompartmental analyses of plasma concen trations, statistical analysis revealed that the presence of fiber (bo th A and B) decreased between 29% and 35% the extent of EE absorbed (r epresented by the pharmacokinetic parameters area under the curve and the maximum plasma concentration) without affecting the rate of the ab sorption process (represented by the time to reach maximum concentrati on and the absorption rate constant).