FORMULATION PARAMETERS OF FLUOROQUINOLONE-LOADED LIPOSOMES AND IN-VITRO ANTIMICROBIAL ACTIVITY

To load pefloxacin and ofloxacin in liposomes, two preparation procedu res were carried out, leading to the formation of multilamellar vesicl es (MLVs) or reverse-phase evaporation vesicles (REVs). MLVs were able to entrap greater amounts of the two drugs than REVs, especially when the drugs were co-dissolved with the lipid mixture in the organic pha se. The encapsulation efficiency was influenced by the presence of a n egatively charged lipid in the liposome composition: the greater the c ontent of charged lipidic compound, the larger is the amount of drug e ntrapped, Among the charged systems, a lmitoylphosphatidylcholine-chol esterol-dihexadecyl phosphate mixture (4:3:4 molar ratio) showed the h ighest trapping capacity. The fluidity of the bilayer could also influ ence the encapsulation efficiency. In fact, the increase in encapsulat ion capacity for the lecithin-cholesterol-dihexadecyl phosphate mixtur e (4:3:4 molar ratio) conformed to the following order: dipalmitoylpho sphatidylcholine > dimyristoylphosphatidylcholine > egg phosphatidylch oline. Variation in pH values led to different encapsulation efficienc y and release rate. In vitro experiments on the antimicrobial activity of the encapsulated fluroquinolones compared to the free drug demonst rated a reduction of at least 50% of the minimal inhibitory concentrat ion.