Issue link: https://www.e-digitaleditions.com/i/870536
Tablets & Capsules September 2017 35 heated outside the fluid bed until they are molten. This molten mixture is then transported through a system of heated tubing and sprayed onto the seed API particles from a heated nozzle. As the API particles are kept at a lower temperature than the melting point of the excipient mixture, the molten droplets wet the API particles and solidify upon contact, forming a homogeneous layer. Once this process is complete, the newly coated particles can be further processed to create the final product. This often involves blending them with more APIs, excipients, and/or flavors. Factors to consider when selecting excipients HMC is particularly well suited to controlling the API release profile. Through the addition of emulsifiers to the excipient mixture, the rate of dissolution and/or release can be adjusted to suit the product's requirements. Despite HMC's many advantages over conventional coating techniques, for many formulators it is a relatively new technology, and care must be taken to ensure that the process parameters and coating excipients are opti- mized to ensure success. HMC requires excipients to be in molten (liquid) form when applied to the API, so the ideal excipients have low melting points, in the range of 60° to 80°C. Ideally, the excipients also have a precise melting point versus melt- ing and softening over a wide temperature range. Any lipid excipients should have Generally Recognized As Safe, or GRAS, status and be well accepted by interna- tional authorities, as well as consumers. Furthermore, the API should have a relatively narrow particle size distribution (200 to 500 microns) so that the coating process is predictable and reproducible, leading to a consistent product and low batch variability. While process optimization—including specifying excipients and emulsifiers—adds an additional step to process development, the result is a unique formulation. Figure 3 Release profiles of uncoated and coated vitamin C formulations Time (h) Dissolution rate (%) 100 80 60 40 20 0 0 1 2 3 4 5 6 7 8 9 Ascorbic acid, coated Ascorbic acid, uncoated Note: Hot-melt coating was used to create the extended-release characteristics. Dissolution testing was performed using the USP II (paddle) apparatus at 75 rpm, 37 °C, and in 900 milliliters of demineralized water.