Issue link: https://www.e-digitaleditions.com/i/581434
C 20 October 2015 Tablets & Capsules tablet coating Evaluation of a continuous-cycled film coater in applying a high- solids coating formulation Charles Cunningham and Jörg Crönlein Colorcon Oliver Nohynek Driam The study described here evaluated the performance of a novel film coating formulation that can be applied at solids concen- trations as great as 35 percent in a continuous-cycled coating process. Four trials were conducted and the coated tablets were assessed for weight gain consistency, color uniformity, surface roughness, and gloss. ontinuous film coating processes can shorten coating times and provide excellent color uniformity because they use shallower tablet beds than the traditional batch process, and the tablets pass through the spray zone more frequently [1]. In traditional batch coaters, as the scale of the coating process increases, the diameter of the coating pan increases, as does the depth of the tablet bed and the number of tablets isolated from the spray zone at any given time. This is a fixed constraint of batch coating processes. Elongated (up to15 feet) continuous coating machines, however, use pans that are half the diameter (or less) of manufacturing-scale batch coaters [2]. Furthermore, the tablet bed depth of elongated coaters is closer to that of laboratory- and pilot-scale batch coating pans. As interest in continuous processing grows, coating equipment man- ufacturers are developing more options for continuous film coating. One machine, Driaconti-T Pharma (Driam, Eriskirch, Germany), is a continuous-cycled coater that combines the attributes of continuous processing with the advantages of small-scale batch production. It achieves this by using a segmented chamber [3]. One potential limitation of continuous coating is the difficulty of applying the requisite amount of coating dur- ing the shorter period that the tablets reside in the pan (typically 10 to 15 minutes). It has been proposed that coating formulations with a high solids concentration (25 percent or more) may mitigate this concern without the need to reduce throughput [4, 5]. The study described here evaluated the performance of a novel film coating formulation that can be applied at solids concentrations as great as 35 percent in a continu- ous-cycled coating process. Methods Equipment. The coating evaluations were conducted in a Driaconti-T Pharma continuous-cycled coating machine (photo next page). The machine is equipped with a perforated, 100-centimeter-diameter rotating drum. The drum, 154 centimeters long, has seven coating chambers spaced 22 centimeters apart that are separated by walls 30 centimeters high. The process begins in a warming hopper that raises the temperature of the tablets as needed and then releases them into the first chamber in "mini-batches." Each mini- batch moves from chamber to chamber after the machine applies the specified amount of film coating. Typically, tablets in each chamber are coated to one-seventh of the target final coating weight gain (WG). Once the tablets are sufficiently coated, pneumatically operated flaps built into the walls separating the chambers open the full width of the chamber, forming a helix that conveys the tablets from one chamber to the next with a single rota- tion of the pan. The flap then closes and the next spray sequence begins. Each of the seven chambers includes a spray gun (Schlick 970 ABC, 1.0-millimeter nozzle tip, Düsen- Schlick, Untersiemau, Germany) mounted so that it sprays directly on the tablets. To deliver the coating dis- persion to the spray guns, the coater uses a bank of seven peristaltic pumps (Watson Marlow, Falmouth, UK)