tailieunhanh - Pharmaceutical Coating Technology (Part 14)

Modified release coatings John SUMMARY Relevant aspects of the composition and performance of modified release coatings are considered in this chapter. Initially, the basic characteristics of multiparticulate systems are described and comparisons are made with the performance of whole tablets intended for modified release. The properties and effects of the polymers and plasticizers which are used in modified release coatings are illustrated with examples from the literature. This further develops the basic treatment of these materials provided in Chapter 2. Additional ingredients peculiar to modified release coatings, such as pore-forming agents, are also described. A section on the structure. | Page 409 14 Modified release coatings John SUMMARY Relevant aspects of the composition and performance of modified release coatings are considered in this chapter. Initially the basic characteristics of multiparticulate systems are described and comparisons are made with the performance of whole tablets intended for modified release. The properties and effects of the polymers and plasticizers which are used in modified release coatings are illustrated with examples from the literature. This further develops the basic treatment of these materials provided in Chapter 2. Additional ingredients peculiar to modified release coatings such as pore-forming agents are also described. A section on the structure and function of modified release films and the mechanism of drug release from the coated particle or tablet is also included. Enteric coatings as a special form of delayed release coating are dealt with in a separate section due to their importance to the industry. The use of enteric coating is described in terms of gastrointestinal pH and the properties of an ideal enteric coating are suggested. The following factors as they affect enteric performance are described in some detail the enteric polymer the film formulation the stability of the film coat and the coating process itself. INTRODUCTION In this section we will be concerned with the coating of tablets and multiparticulate systems with the objective of conferring on the dosage form a release characteristic that it would not otherwise possess. The USP has defined a modified release dosage Page 410 form as one for which the drug release characteristics of time course and or location are chosen to accomplish therapeutic or convenience objectives not offered by conventional dosage forms . One particular variant of a modified release dosage form that is the enteric or delayed release form will be dealt with in the subsequent section. As the coating is designed to perform a function critical to the .