title: Physicochemical aspects of the coformulation of colistin and azithromycin using liposomes for combination antibiotic therapies.
abstract: Remote loading of azithromycin into liposomes, and subsequent release behavior in the presence of colistin, has been investigated with a view to understand the potential of liposomes to enable the coformulation of these two antibiotics for application in inhalation therapy. Azithromycin was successfully encapsulated into liposomes by remote loading (encapsulation efficiency > 98%). Slow release of azithromycin was achieved in the presence of cholesterol in a concentration-dependent manner, with a 4:1 mol ratio of phospholipid-cholesterol releasing 22% azithromycin in 24 h, whereas a 2:1 mol ratio released only 4.9% of azithromycin in 24 h. Addition of colistin to the formulation with increasing concentration did not change the loading behavior, but accelerated drug release, increasing the percentage of released azithromycin from 4.9% to 30% over 24 h. The permeabilizing ability of colistin on liposomes is consistent with its permeabilizing effect on bacterial cells. This behavior opens opportunities to tailor the release rate of drugs coformulated with colistin using liposomes as the carrier.
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville Campus), Parkville Victoria 3052, Australia.
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Wallace
authors.forename: Roger L
authors.initials: RL
authors.lastname: Nation
authors.forename: Jian
authors.initials: J
authors.lastname: Li
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Boyd
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000737:chemistry; D017963:Azithromycin / Q000008:administration & dosage* / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D002784:Cholesterol / Q000737:chemistry; D003091:Colistin / Q000008:administration & dosage* / Q000737:chemistry; D003102:Colloids / Q000737:chemistry; D003692:Delayed-Action Preparations / Q000737:chemistry; D004355:Drug Stability; D008081:Liposomes / Q000737:chemistry* / Q000648:ultrastructure; D014462:Ultrafiltration
chemical_list: D000900:Anti-Bacterial Agents; D003102:Colloids; D003692:Delayed-Action Preparations; D008081:Liposomes; D017963:Azithromycin; D002784:Cholesterol; D003091:Colistin