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22 October 2015 Tablets & Capsules mounted on a cart at the machine's front. Each pump is controlled separately, which allows sequencing of the spray guns as the chambers fill during startup and as they empty during shutdown. If desired, the separate controls can be used to apply different WGs at each chamber or apply two different coatings in the same process. For instance, a gloss coat could be applied in the final cham- ber. Figure 1 illustrates the machine's configuration and the photo on page 20 shows the coating chambers. The multi-chamber configuration, coupled with indi- vidual spray gun control, also allow researchers to run trial batches in a single chamber to understand how dif- ferent parameter settings affect performance before scal- ing up to full production. Coating formulation and preparation. The study used a new, pigmented coating formulation developed by Colorcon and based on a polyvinyl alcohol-polyethylene glycol graft copolymer (Kollicoat IR, BASF, Florham Park, NJ). This developmental coating system, designed for aqueous application at high solids concentrations, exhibits very low viscosity (Figure 2). Typically, it is rec- ommended that coating formulations not exceed 450 to 500 centipoise so that they can be easily pumped and so that they form adequate droplets. For each trial— depending on the specified solids concentration—the fully formulated dry powder mix was added to water using a standard propeller mixer with moderate agitation. Once all the powder was added to the water, the impeller's speed was reduced and the coating was gently mixed for 30 minutes before use. Coating trials and parameters. Four trials were con- ducted to assess how increasing the coating's solids con- centration affected throughput, coating uniformity, and tablet surface properties. Round, 10-millimeter placebo tablets weighing 300 milligrams and debossed with Colorcon's logo were used in the trials. The target coat- ing WG was 3.0 percent. As the solids concentration of the coating formulation for each trial increased, tablet throughput was increased proportionally to achieve the target WG. All other coating parameters were held con- stant (Table 1). Coating uniformity assessments. Tracer tablets were used to determine coat- ing WG and variation as the mini-batches of tablets passed through the coating chambers. Each tracer tablet bore a unique letter and number written with a black marker. The marked tablets were dried to a constant weight in a 50°C oven. After drying, the weight of each tablet was recorded. For each trial, the coating process was allowed to run Driam's Driaconti-T Pharma Figure 1 Driaconti-T Pharma configuration Figure 2 Viscosity profile of the coating formulation 500 450 400 350 300 250 200 150 100 50 0 15 20 25 30 35 40 Limit of desirable viscosity for film coating Coating solids concentration (%) Viscosity (cP) Visually, tablets bearing a higher-solids coating were virtually indistinguishable from those coated with a lower-solids formulation.