Liposomes and Lipid Structures as Carriers of Amphotericin B

Abstract

Almost 25 years ago, Bangham noted that “smectic mesophases” formed when biological lipids were dispersed in aqueous media (1). These structures, later described as multilamellar liposomes, consisted of concentric biomolecular lamellae of lipid, each separated by an aqueous compartment. Although important as models of cellular membranes, the potential of these systems as drug carriers was not lost. It was quickly recognized that water-soluble drugs could be entrapped within the aqueous spaces of the vesicles, while hydrophobic drugs would intercalate into the lipid layers. The more recent development of preparative techniques allowing control over the size, lamellarity, trapped aqueous volume and solute distribution in the final emulsions has led to a rapid expansion in this field (2). In fact, the emergence of liposomes as drug delivery vehicles is now extensively documented (3). Liposome-dependent alterations in pharmacokinetics/pharmacodynamics have been well described for a variety of biologically active compounds. Perhaps far more remarkable, however, have been the reports that certain liposome formulations are also able to attenuate toxicities of associated drugs without substantially compromising efficacy (4). One drug affected in this manner is amphotericin B.