Tamilvanan S
Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research, Sector-67, S.A.S. Nagar, Punjab 160062, India.
Prog Lipid Res. 2004 Nov;43(6):489-533. doi: 10.1016/j.plipres.2004.09.001.
Lipid emulsions (LEs) are heterogenous dispersions of two immiscible liquids (oil-in-water or water-in-oil) and they are subjected to various instability processes like aggregation, flocculation, coalescence and hence eventual phase separation according to the second law of thermodynamics. However, the physical stability of the LE can substantially be improved with help of suitable emulsifiers that are capable of forming a mono- or multi-layer coating film around the dispersed liquid droplets in such a way to reduce interfacial tension or to increase droplet-droplet repulsion. Depending on the concentrations of these three components (oil-water-emulsifier) and the efficiency of the emulsification equipments used to reduce droplet size, the final LE may be in the form of oil-in-water (o/w), water-in-oil (w/o), micron, submicron and double or multiple emulsions (o/w/o and w/o/w). The o/w type LEs (LE) are colloidal drug carriers, which have various therapeutic applications. As an intravenous delivery system it incorporates lipophilic water non-soluble drugs, stabilize drugs that tend to undergo hydrolysis and reduce side effects of various potent drugs. When the LE is used as an ocular delivery systems they increase local bioavailability, sustain the pharmacological effect of drugs and decrease systemic side effects of the drugs. Thus, the rationale of using LE as an integral part of effective treatment is clear. Following administration of LE through these routes, the biofate of LE associated bioactive molecules are somehow related to the vehicles disposition kinetics inside blood or eyeball. However, the LE is not devoid from undergoing various bio-process while exerting their efficacious actions. The purpose of this review is therefore to give an implication of LE for parenteral and ocular delivering systems.
脂质乳剂（LEs）是两种互不相溶的液体（水包油或油包水）的非均相分散体系，根据热力学第二定律，它们会经历各种不稳定过程，如聚集、絮凝、聚结，最终导致相分离。然而，借助合适的乳化剂可以显著提高LE的物理稳定性，这些乳化剂能够在分散的液滴周围形成单层或多层涂膜，从而降低界面张力或增加液滴间的排斥力。根据这三种成分（油-水-乳化剂）的浓度以及用于减小液滴尺寸的乳化设备的效率，最终的LE可能呈水包油（o/w）、油包水（w/o）、微米、亚微米以及双重或多重乳液（o/w/o和w/o/w）的形式。o/w型LE是胶体药物载体，具有多种治疗应用。作为静脉给药系统，它可包载亲脂性的水不溶性药物，稳定易水解的药物，并降低各种强效药物的副作用。当LE用作眼部给药系统时，它们可提高局部生物利用度，维持药物的药理作用，并降低药物的全身副作用。因此，将LE用作有效治疗的一个组成部分的基本原理是明确的。通过这些途径给予LE后，与LE相关的生物活性分子的生物命运在某种程度上与血液或眼球内载体的处置动力学有关。然而，LE在发挥其有效作用时并非不会经历各种生物过程。因此，本综述的目的是阐述LE在胃肠外和眼部给药系统中的意义。
