The purpose of this study was to investigate the effects of particle shape on the movement of particles in a pan-coating device using novel video-imaging techniques. An area scan CCD camera was installed inside a 24-in pan coater at the same location as that of a spray nozzle, and the movement of particles was tracked using machine vision. A white tracer particle was introduced inside a bed of black-coated particles. The effects of pan loading, pan speed, and particle shape on the movement of particles was studied. The response variables were circulation time, surface time, projected area of particle per pass, dynamic angle of repose, cascading velocity, and dispersion coefficient. Experiments were conducted at 3 different pan speeds, 6, 9, and 12 rpm, and 2 fill levels (ratio of bed depth to pan diameter), one eighth and one quarter, and data were collected over a 30-minute time period.

The purpose of this study was to evaluate the change of surface roughness and the development of the film during the film coating process using laser profilometer roughness measurements, SEM imaging, and energy dispersive X-ray (EDX) analysis. Surface roughness and texture changes developing during the process of film coating tablets were studied by noncontact laser profilometry and scanning electron microscopy (SEM). An EDX analysis was used to monitor the magnesium stearate and titanium dioxide of the tablets. The tablet cores were film coated with aqueous hydroxypropyl methylcellulose, and the film coating was performed using an instrumented pilot-scale side-vented drum coater. The SEM images of the film-coated tablets showed that within the first 30 minutes, the surface of the tablet cores was completely covered with a thin film.

The objective of this study was to investigate the anion-controlled drug release mechanism through the cationic coating polymer Eudragit RS 30 D as a function of the anion attraction toward the polymer’s quarternary ammonium group (QAG), anion valence, and film composition. The mechanism was investigated by dissolution testing, determination of chloride ion exchange using ion chromatography, plasticizer leaching by means of differential scanning calorimetry, and water uptake by Karl Fischer titration. All experiments were performed on coated theophylline micro tablets or isolated films of various compositions using 0.01 M sodium nitrate, sodium sulfate, disodium succinate, sodium acetate, and succinic acid as dissolution media. The mechanism of drug release involved an immediate penetration of dissolution medium into the polymer followed by an instant exchange of chloride against the medium’s anion species at completely different rates compared with the drug release.

AbstractA newly available polyvinylacetate aqueous dispersion, Kollicoat SR 30D, was evaluated with respect to its ability to modulate the in vitro release of a highly water-soluble model compound (diphenhydramine hydrochloride) from nonpareil-based systems. Kollicoat SR 30D premixed with a selected plasticizer (10% wt/wt propylene glycol, 2.5% triethyl citrate, or 2.5% dibutyl sebacate), talc, and red #30 lake dye was coated o­nto the drug beads in an Aeromatic Strea I fluid-bed drier with a Wurster insert using bottom spray. With propylene glycol as the plasticizer, increases in polymer coating level retarded drug release from beads in a stepwise fashion along with apparent permeability, indicating a consistent release mechanism. Stability studies at 40°C/75% RH revealed gradual decreases in dissolution rate, and additional curing studies further confirmed the dependence of release kinetics o­n curing condition.

The film forming and coating properties of Glycerol ester of maleic rosin (GMR) and Pentaerythritol ester of maleic rosin (PMR) were investigated. The 2 rosin-based biomaterials were initially characterized in terms of their physicochemical properties, molecular weight (Mw), and glass transition temperature (Tg). Films were produced by solvent evaporation technique o­n a mercury substrate. Dibutyl sebacate plasticized and nonplasticized films were characterized by mechanical (tensile zzzz strength, percentage elongation, and Young's modulus), water vapor transmission (WVT), and moisture absorption parameters. Plasticization was found to increase film elongation and decrease the Young's modulus, making the films more flexible and thereby reducing the brittleness. Poor rates of WVT and percentage moisture absorption were demonstrated by various film formulations.

The specific aim of the present study was to investigate the biodegradation and biocompatibility characteristics of rosin, a natural film-forming polymer. Both in vitro as well as in vivo methods were used for assessment of the same. The in vitro degradation of rosin films was followed in pH 7.4 phosphate buffered saline at 37°C and in vivo by subdermal implantation in rats for up to 90 days. Initial biocompatibility was followed o­n postoperative days 7, 14, 21, and 28 by histological observations of the surrounding tissues around the implanted films. Poly (DL-lactic-co-glycolic acid) (PLGA) (50:50) was used as reference material for biocompatibility. Rate and extent of degradation were followed in terms of dry film weight loss, molecular weight (MW) decline, and surface morphological changes. Although the rate of in vitro degradation was slow, rosin-free films showed complete degradation between 60 and 90 days following subdermal implantation in rats.

Rai, R.; Collum, D.B. Tetrahedron Lett.
1994, 35, 6221.

Abstract

Amylose-ethylcellulose film coatings obtained from organic-based solvents were investigated as potential vehicles for colonic drug delivery. Amylose, in the form of an amylose-butan-1-ol dispersion, and ethylcellulose, dissolved in either ethyl lactate, ethanol, or propanol and plasticized with dibutyl sebacate, were mixed in various proportions and applied using a fluidized bed coater to achieve a range of film thicknesses o­n 5-aminosalicylic acid pellets. Drug release from the coated pellets was assessed under gastric and small intestinal conditions in the presence and absence of pepsin and pancreatin using dissolution methodology, and also within a simulated colonic environment involving fermentation testing with human feces in the form of a slurry. Under upper gastrointestinal tract conditions, the rate and extent of drug release were found to be related to the thickness of the coating and the ratio of amylose to ethylcellulose within the film.

The goal of this study was to determine which combination of excipients would result in a tablet core that would be suitable for use in an aqueous enteric film-coating process. A relatively simple formulation of microcrystalline cellulose (MCC) and partially pregelatinized starch (P-PGS) was found to provide the necessary properties.MCC in the formulation provides the compactability needed to produce a tablet that will withstand the mechanical stresses of the film-coating process. P-PGS provides the dissolution characteristics and is responsible for the stability characteristics in this moisture-sensitive, enteric film-coated application. It was also found that P-PGS could be used to reduce the deleterious effects of superdisintegrants in formulations.


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Latex dispersions have proved to be very useful in aqueous-based film coating, especially in controlled-release applications. Film coatings commonly are colored with pigments to provide a means of product identification and to enable the manufacturer to distinguish similar products. Colored films allow the manufacturer to impart a distinct appearance to the dosage form, which is useful from a marketing standpoint. The use of pigments in film coatings also facilitates patient recognition and makes the product aesthetically appealing. Because both the latex polymer and pigment particles exist in the colloidal or near-colloidal state, interactions caused by surface properties may sometimes lead to unstable formulations. This article examines some of the issues that are important to consider when formulating latex dispersions with pigments.