![[Article Title]](https://media.tabletscapsules.com/m/54/article/595441.jpg)
Film coating is undertaken for numerous reasons: improving the appearance of the tablet, protecting the tablet from light and moisture, to protect the stomach lining from aggressive formats and to control and engineer drug release. It is therefore vital that the tablet coating needs to be uniform, irrespective of the batch size. Whether a base range of 100,000 tablets to 1 million+, every tablet must be coated to the same extent. There are a number of steps one can take to control uniformity: establish production parameters, implement in-process testing—including visual inspections, and create a defined endpoint.
There are a number of factors and processes involved including air inlet (temperature and humidity), spray rates and drying. Additionally, the tablet surface area and batch size are calculated at product design stage, to determine the amount of polymer required. The formulation is then developed according to specifications. Once those parameters have been set, greater accuracy can be achieved to avoid any possible defects, by carrying out in-process testing and considering additional coating suspension requirements to ensure the coating end point is reached.
Then a visual inspection is undertaken to monitor for defects, such as chipping, logo bridging, smudged coating, peeling, over-wetting or layer separation. Anything not meeting Acceptable Quality Levels (AQL) is considered sub-standard. If a visual inspection to eradicate any defective tablets is set to 5%, this figure will be increased to guarantee the required accuracy.
Finally, the endpoint of the film coating process can be determined by weighing the tablet samples periodically throughout the coating operation. This determines the average tablet weight gain and stops the coating process when the tablets have reached the target weight. This approach assumes that the tablet weight gain reflects the proportionate deposition of coating material. The end point can also be controlled by the tablet appearance, as per the visual inspection, where the coating dispersion is deemed complete - forming part of the overall process and not culminating in one sharp end point per se.
At the end of the day, the aim to is produce a batch with zero defects, in order to support patient compliance, brand reputation and costly production losses. This can be achieved by focusing on optimizing coating efficiencies, and therefore overall production. Setting parameters, testing, analyzing, and interpreting controlled tests based on risk analysis helps achieve the desired 100% accuracy.
Prashant Deshpande, Head, Process & Technology Support, ACG Engineering, https://www.acg-world.com/en_us/