International Journal of PharmTech Research CODEN( USA): IJPRIF ISSN : 0974-4304 Vol.1, No.2, pp 235-240 April-June 2009 Aqueous-based Film coating of Tablets: Study the Effect of Critical Process Parameters J. K. Patel*, A. M. Shah # and N. R. Sheth + *Nootan Pharmacy College, Visnagar, Gujarat,India. # K.N.V. Pharmacy College, Metoda, Rajkot, Gujarat, India. + Department of Pharmaceutical Science, Saurashtra University, Rajkot, Gujarat, India. E-mail: jayvadan04@yahoo.com Abstract :The aim of the present work was to study the effect of various process parameters on an aqueous-based film coating process of tablets performed in a side-vented perforated pan-coating apparatus. Results of preliminary trials indicate that spray rate, inlet air temperature, percentage solid content, atomizing air pressure and speed of rotation affected characteristics of coating. A 3 3 full factorial design was employed to study the effect of independent variables; spray rate (X 1 ), inlet air temperature (X 2 ) and rotating speed of pan (X 3 ) on dependent variables: coating uniformity, coating process efficiency, surface roughness and percentage loss on drying. The best batch exhibited spray rate of coating solution 8 gm/min, inlet air temperature 55°C and rotating speed of pan 12 rpm. The surface characteristics of the aqueous-based film-coated tablet were studied under a scanning electron microscope. Keywords: Aqueous film coating, 3 3 full factorial design, process parameters. Introduction Aqueous film coating is applied as a thin polymeric film to the surface of a tablet. Film coating can protect the tablet from light, temperature and moisture, mask undesirable taste or odor, improve the appearance, provide tablet identity, facilitate swallowing and control or modify the release of the drug (1-2) . Aqueous coating of oral solid dosage forms has rapidly replaced solvent- based coatings for safety, environmental and economic reasons. However, since tablets may contain moisture- sensitive drugs or excipients, the use of water raises concerns about the physical and chemical stability of the coated tablets (3) . Film-coating of tablets is a multivariate process, with many different factors, such as coating equipment, process conditions, composition of the core tablet, shape of tablets, coating liquid etc., which affect the pharmaceutical quality of the final product. The side-vented, perforated pan coater is the most commonly used coating device of tablets. So process parameters are highly affecting the quality of final product. High quality aqueous film coating must be smooth, uniform and adhere satisfactorily to the tablet surface and ensure chemical stability of a drug (4) . Atomizing air pressure is also affecting the surface property of coated tablets (5-6) . The spray rate is an important parameter which affects the moisture content of the formed film and subsequently, the quality and uniformity of the film (7-9) . The inlet air temperature affects the drying efficiency (i.e. water evaporation) of the coating pan and the uniformity of coatings. In the aqueous film coating process, tablets are exposed to wide temperature range and humidity variations that may promote undesired water penetration into the tablet core during coating or storage. Penetrated water can cause changes in the structure of the film core interface, core expansion and increase the risk of degradation of a moisture-labile drug. Wide variations in the amount of coating received by individual tablets within a batch may also have some effect on the dissolution rate of drug even from immediate-release tablets (9) . It also affects the amount of moisture content of the core tablets. And moisture content increase the degradation of drugs (9-10) . Rotating speed of pan affect the surface property and coating uniformity (11-13) . Percentage solid content generally affects the tablet surface and coating efficiency (14) . The aim of the present work was to study the effect of various process parameters on an aqueous-based film coating process of tablets performed in a side-vented perforated pan-coating apparatus. Experimental Materials Opadry II 31 (G 51557) was obtained as gift sample from Colorcon (Mumbai, India). The core tablet composed of colloidal silicon dioxide was obtained as gift sample from Cabot Sanmar Ltd. Dibasic calcium phosphate dihydrate was procured from Canbera Chemical. Hydroxyl Propyl Methyl Cellulose-K4M wase procured from Dow Chemicals. All other ingredients were analytical grade.