Recent Advances in the Use of Phospholipid Excipients in Local or Injectable Depot Formulations

Several drugs have a short biological half-life and multiple administrations are needed to achieve a therapeutic effect. In addition, such drugs may not be suitable for oral administration because of degradation in the gastrointestinal tract and poor permeation through the gastrointestinal tract epithelium. Typical examples are high molecular weight proteins and peptides. For this sort of drugs, slow release (depot) injections or local depot formulations (e.g. via inhalation) would enable a more patient-friendly, low frequency therapy which reduces the risk for possible toxic plasma peak concentrations. In the past, sustained drug release has been successfully achieved over short time intervals by means of e.g. oily drug suspensions. Depot injectables based on biodegradable polymers like poly(lactidco-glycolic)acid (PLGA) may enable drug release over an interval of up to several months. In order to design injectable depot formulations with intermediate drug release intervals or local depot formulations, lipid- and especially phospholipid-based formulations are nowadays investigated and developed. This article describes recent advances achieved with phospholipid-based formulations for systemic and local extended drug release.