USE AND CHARACTERISTICS OF A NOVEL LIPID PARTICLE-FORMING MATRIX AS A DRUG-CARRIER SYSTEM

The concept and design of a novel drug-delivery system, Biosomes, are described. The system consists of a lipid matrix and a bioactive material (drug) and is based on a mixture of naturally occurring lipids, both polar and nonpolar, which form a partly ordered phase. The lipid system, which is essentially water-free but may contain up to 50% water by weight, can incorporate both hydrophilic and hydrophobic drug compounds depending on the relative composition of polar and nonpolar lipids. An important intrinsic feature of the system is the instability in excess water which results in spontaneous formation of lipid particles, named Biosomes, containing the drug compounds which provide for the release of the bioactive material in vivo. The system is applicable for oral and parenteral administration as well as for enhancing dermal, rectal and nasal absorption of drugs. In this communication the general physicochemical properties of a system composed of phosphatidylcholine from soybean and medium-chain monoacylglycerol and its ability to incorporate model drugs are viewed. The importance of using well-defined lipids when formulating the lipid matrix is also discussed. Low-molecular-weight heparin (LMWH), used in the treatment and prevention of thromboses, is one of the model drugs utilized in the development of the system due to its poor oral absorption. The biological benefits of the system were demonstrated by studies in rabbits: a substantially improved bioavailability of LMWH was obtained when the drug was incorporated into an appropriate lipid matrix and given intraduodenally whereas virtually no effect was observed for an aqueous solution or a system based on crude, unpurified lipids.