Coating Articles

The coating of particles, agglomerates, and compacts is an important operation in the pharmaceutical, food, and chemical industries. Various types of equipment have been used for such a purpose, including rotating pans, fluidized beds, and spouted beds (1–4). This article describes the Wurster system, a high-velocity, circulating-bed unit widely used for coating pharmaceutical pellets and tablets. Figure 1 shows a schematic diagram of a Wurster coating unit. The system typically consists of a relatively short cylindrical column with a truncated conical chamber base, a cylindrical insert (draft tube) in the center of the chamber, and a centrally located air distribution plate below the conical base. A spray nozzle, located in the center of the air-distribution plate, enables the introduction of coating solutions and suspensions.

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Aqueous enteric coating systems have been widely used for many years and offer substantial advantages over solvent systems, particularly with regard to environmental and toxicological concerns. Although these formulated aqueous enteric coating systems were an advancement from traditional solvent systems, they required the separate addition of plasticizers, detackifiers, pigments, and other process aids (1). Through the years, little reduction has taken place in the complexity of these systems (2). Selection of the optimal additives for each formulation adds time to the development of individual formulations (3–5).Multiple,  time-consuming steps also are required in the preparation of these aqueous enteric coating dispersions (6). In addition, many of these systems are provided as liquid dispersions, which can be problematic when handling, transporting, and controlling storage conditions.

Abstract

Keywords:  diphenhydramine hydrochloride, Kollicoat SR 30D, nonpareil, polyvinylacetate, sustained release

Abstract

Abstract

Abstract  :This study investigates the crystallization of the endogenous surfactant nonoxynol 100 in Eudragit NE30D-free films during storage and the influences of nonoxynol 100 on the dissolution of diphenhydramine hydrochloric acid (HCl) pellets coated with Eudragit NE30D before and after aging at ambient conditions. Polarizing light microscopy showed that when Eudragit NE30D-free films were stored at ambient conditions, off-white, flower-shaped crystals formed and increased in the polymer film as storage time increased. Also, x-ray diffraction showed polymer crystals in the aged free film. Thermogravimetric analysis showed no evidence of combined volatile molecules with the polymer molecules, and Fourier transformed infrared spectroscopy (FTIR) data suggested the same chemical composition of the polymer before and after phase separation.