ABSTRACT
The pharmacological efficacy of parenterally administered drugs is dependent on their distribution throughout the body as well as the elimination route and kinetics. More effective and safe drug action may be achieved by accumulating the active substance at the target site while reducing its systemic levels. Among several strategies for controlling the pharmacokinetics of parenterally administered therapeutic substances, drug incorporation into submicroscopic biodegradable drug carriers has been one of the most extensively investigated [1-9]. These carriers include oil-in-water nanoemulsions, liposomes, and nanoparticles. Nanoparticles are solid bodies in the submicronial size range, usually made of polymers. Depending on their composition nanoparticles may be divided in two major classes: nanospheres and nanocapsules. Nanospheres are composed of a solid matrix, whereas nanocapsules have a characteristic core-shell structure. The drug may be chemically bound to the particle-forming polymer, adsorbed to the nanoparticle surface or entrapped in the nanoparticle. In the latter case, it may be either dissolved in the nanocapsule liquid core or dispersed in the nanosphere matrix. Recently drug nanosuspensions showing potential as a new class of injectable nanoparticulate formulations have been developed and described [10]. To date the intensive research in the field of polymer-based particulate drug carriers for parenteral drug delivery has yielded only a few microparticulate products, whereas nanoparticulate formulations for therapeutic uses have not yet appeared on the market, apparently reflecting the difficulty in developing a formulation process capable of producing nanoparticles acceptable from a regulatory standpoint.
