文档介绍：advanced
drug delivery
reviews
ELSEVIER Advanced Drug Delivery Reviews 25 (1997) 47-58
Formulation of self-emulsifying drug delivery systems
Colin W. Pouton”
School ofPharmacy and Pharmacology, Univrrsity ofBath, Claverton Down, Bath BA2 7AY, UK
Abstract
Self-emulsifying drug delivery systems (SEDDS) are mixtures of oils and surfactants, ideally isotropic, sometimes
including cosolvents, which emulsify under conditions of gentle agitation, similar to those which would be encountered in
the gastro-intestinal tract. Hydrophobic drugs can often be dissolved in SEDDS allowing them to be encapsulated as unit
dosage forms for peroral administration. When such a formulation is released into the lumen of the gut it disperses to form a
tine emulsion, so that the drug remains in solution in the gut, avoiding the dissolution step which frequently limits the rate of
absorption of hydrophobic drugs from the crystalline state. Generally this can lead to improved bioavailability, and/or a
more consistent temporal profile of absorption from the gut. Ultra-low oil-water interfacial tension and/or substantial
interfacial disruption are required to achieve self-emulsification. SEDDS are usually formulated with triglyceride oils and
ethoxylated nonionic surfactants, usually at surfactant concentrations greater than 25%. In practice, disruption of the
oil-water interface is caused by ration of water into the formulation or diffusion of cosolvents away from the
formulation. Both of these phenomena can be studied using equilibrium phase diagrams, which bination with particle
size measurements allow the optimisation of performance of SEDDS. The precise mechanisms of emulsification remain the
subject of speculation but there is an empirical link between self-emulsification, liquid crystal formation, oil-water
phase-inversion temperature and enhanced solubilization of water by oily formulations, and these phenomena are indicators
of the effici