Tablets & Capsules


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eye on In the study discussed here, we assessed the ability of a coating for- mulation to be applied over a rela- tively broad range of product-bed temperatures. Purpose The goal of the study was 1) to determine whether a tablet film coat- ing based on a modified pea-starch polymer in a ready-to-use formulation [3-5] could be processed at bed tem- peratures lower than 25°C and 2) to evaluate the coating quality when compared to processing it at elevated temperatures. Materials and methods To begin, 2.5 kilograms of tablet cores (335 milligrams, mannitol-based) were processed with a 20 percent dry solids aqueous coating formulation [1] until they gained 4 percent in weight. Coating took place in a fully perfo- rated 4-liter coating pan (photo) equipped with a Schlick spray gun that used a 1.0-millimeter fluid tip and an ATB air cap [6]. Coating trials The parameters listed in Table 1 were selected based on the authors' experience applying other commer- cially available aqueous coatings. These parameters were used for the first trial to establish a benchmark against which to evaluate the modified pea-starch-based coating. Unfortunately, the coated tablets that resulted had an unacceptable appearance (photo next page). The "picking" defect that occurred was determined to have arisen from a reduc- tion in effective airflow through the tablet bed and, possibly, from tablets moving too slowly through the spray zone. Upon further investigation, it was found that inadequate sealing/posi- tioning of the exhaust duct allowed process drying air to bypass the prod- uct bed and exit the coating pan with- out drying the product (Figure 1). Tablets & Capsules January 2017 41 Timothy J. Smith and Ryan Crawford Freund-Vector Carmen Popescu Roquette America Grégory Le Bihan, Sébastien Croquet, Xavier Parissaux, and Philippe Lefèvre Roquette excipients This edition of the column discusses the results of a study in which a film coating that includes a novel polymer was applied at low bed temperatures. When tablets that include a mois- ture-sensitive active pharmaceutical ingredient (API) require a coating, aqueous film coatings based on poly- ethylene glycol (PEG), polyvinyl alco- hol (PVA), or hydroxypropyl methyl- cellulose (HPMC) are used. These coatings are applied at high product temperatures to quickly remove mois- ture so that it doesn't degrade the API. Unfortunately, that approach can lead to heat degradation of the API and cause physical defects in the coating [1, 2]. Many elements influence the film coating process and a successful process must keep many factors in balance, not just temperature. Nonetheless, these factors can be simplified to the follow- ing three areas of concern: • Wetting conditions -Solution properties (percentage solids, viscosity, film formation temperature range, and tackiness) -Solution application (spray rate, spray zone/area, spray droplet size, and gun-to-bed distance) • Drying conditions (airflow, tempera- ture/heat capacity of the drying air, and the efficiency of air flowing through the tablet bed) • Product movement (tablet size and shape, coating pan rotational speed, and baffle design). The coating equipment used in the study [6]

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