Issue link: https://www.e-digitaleditions.com/i/1101841
18 April 2019 Tablets & Capsules (sprayed at 12.5 percent w/w solids) to that of an inter- mediately high-solids film coating formulation (Aquarius Preferred HSP, sprayed at 20 percent w/w solids) and an ultra-high-solids film coating formulation (Aquarius Genesis, sprayed at 35 percent w/w solids). As the figure shows, the processing time required to achieve a 3 percent weight gain went from 120 minutes at 12.5 percent solids to 70 minutes at 20 percent solids to 38 minutes at 35 percent solids [1]. This reduced pro- cessing time can not only improve process economics, but it also reduces the tablets' exposure to potentially stressful conditions such as relatively high processing temperatures and mechanical agitation. Also, the shorter processing time did not compromise product quality, as indicated by the tablet samples shown in Figure 2. These results are primarily due to advances in polymer science that have allowed for a substantial reduction in coating suspension viscosity, as shown in Figure 3. Another important benefit of reduced processing time is that it allows for a continuous coating process. Large- volume continuous coating processes (capable of achiev- ing throughputs of 500 to 2,000 kg/h) have been in oper- ation in a somewhat limited fashion for more than a decade. More recently, the pharmaceutical industry has begun to shift its focus toward fully continuous manufac- turing processes, which require coating process through- puts in the range of 40 to 120 kg/h. Existing coating machines such as the O'Hara FCC 75, GEA ConsiGma, and others are capable of achieving these throughput rates, and available high-solids coatings can support this industry trend as well. A challenge of conducting development programs capable of supporting large-throughput coating pro- cesses is that companies typically have a limited amount of material available for the development process. One way to address this challenge is to configure a batch coater as a surrogate for the continuous process. For example, the O'Hara FCC 500 continuous coater uses a pan of similar diameter (19 inches) to those available for an O'Hara LabCoat IIX coater. Reconfiguring the latter to accommodate reduced bed depths and the process air- flows and spray rates commensurate with those used in a segment of the FCC 500 can produce a suitable model for product development. Table 1 shows the processing times for various coatings applied using a LabCoat IIX fitted with a 19-inch pan and configured to simulate a segment of the FCC 500. The reduced process times are indicative of the potential throughput-rate increases such coatings can achieve. Figure 4 shows the coating data for a continuous coater designed to support a continuous manufacturing process (GEA ConsiGma), using the Aquarius Genesis film coating at 35 percent solids [2]. The coater in this case is capable of attaining a throughput rate of 100 to 120 kg/h, with an individual sub-batch process time of 5 to 6 minutes. As the data show, the process can achieve a visually uniform coating with a weight gain of only 2 percent (because at 2 percent, the color difference [∆E] Table 1 Coating process time for 3 percent weight gain (O'Hara LabCoat IIX coater with a 19-inch pan configured to simulate a segment of an O'Hara FCC 500 continuous coater) Coating Solids (%) Time (minutes) Aquarius Prime 12.5 22 Aquarius HSP* 20 11 Aquarius Genesis 35 5 * Achieved a throughput rate of 450 kg/h in an FCC 500 continuous coater Figure 3 Typical viscosity profiles of evaluated coatings 1,600 1,400 1,200 1,000 800 600 400 200 0 10 15 20 25 30 35 40 Suspension viscosity (cP) Solids concentration (% w/w) Aquarius Prime Aquarius HSP Aquarius Genesis Desirable limit Figure 4 Visual coating uniformity for coating sprayed at 35 percent solids using a GEA ConsiGma coater (N=20) Weight gain (%) 5 4 3 2 1 0 4 3.5 3 2.5 2 1.5 1 0.5 0 0 1 2 3 4 Visually discernable limit for yellow color used (∆E<3) Coating time (minutes) Color difference (∆E)