Phospholipids in Drug Delivery Systems

The main aim in drug delivery systems, is to increase drug bioavailability at specific time and location of the body, the ability to maintain a relatively constant drug concentration in the specific period of time, adjustable release rate of the drug, the ability to deliver multiple drug substances, increasing the efficiency and reducing the side effects on the other non-diseased host tissues. Some therapeutic agents such as proteins/peptides, nucleic acids, anti-carcinogens, and other drugs, used nowadays, may have the drawbacks of low bioavailability, rapid clearance, high toxicity and very harmful side effects. The invention of drug delivery and drug carriers has created a revolution in the treatment of many diseases which is increasing in progress. Phospholipids are compounds with bipolar nature due to the presence of phosphate group, a hydrophilic head and two lipophilic branches. Phospholipids can carry hydrophilic and hydrophobic pharmaceutical compounds in a structure compatible with living cells and serve their penetration in living cells and into the target cell. Phospholipids as surface-active wetting agents cover the surface of crystals to enhance the hydrophilicity of hydrophobic drugs and higher efficiency in drug delivery. In this paper, studies are extended to different kinds of phospholipids, their structures, their sources, physical properties, their complexes with drugs, phospholipid micelles and effective factors in their selection for drug delivery systems.