In vivo evaluation of microparticles for polymyxin B oral administration

Calcium alginate/chitosan microparticles for polymyxin B (PMB) oral administration, FITC labelled and previously in vitro and ex vivo characterised, were assayed in vivo by animal model, male rats Wistar, in accordance with the European Community regulations. PMB (125 mg/kg) in both water solutions and microsystem water suspensions as well as a corresponding water volume (2 ml) were administered by oral gavage to three groups of fed animals. Six animals for each group were sacrificed after 24 h, 48 h and 72 h. Urine, blood and intestine samples were collected, whereas other organs were morphologically observed. PMB levels were determined on serum obtained from blood and on Peyer’s patches from intestine by a microbiological agar well diffusion method using E. coli as indicator strain. Moreover, Peyer’s patches were examined by fluorescence confocal microscopy. Fluorescent microparticles were found inside Peyer’s patches from all animals dosed with the microsystem, unlike controls. PMB was significantly detected in serum samples of all the animals dosed with the microsystem and in urine samples at 72 h after dosing. The microparticles resulted suitable to be taken up by Peyer’s patches and to be translocated to the systemic circulation via the limphatics.