Issue link: https://www.e-digitaleditions.com/i/807837
F Tablets & Capsules April 2017 25 coating Tips to improve tablet coating efficiency Chris Byers Solid Dose Solutions Most manufacturers consider their film coating process to be efficient because it's validated and produces consistent product quality. But neither addresses process efficiency. This article identifies common sources of inefficiency and how to fix them. ilm coating materials are expensive, and wasting them just adds to their cost. Nonetheless, very few companies compare the amount of solids sprayed with the weight gain of coated products. Nor do they factor in the cost to dispose of the solids that end up in the dust collector. In my experience, it costs about $1,250 to buy and dispose of 25 kilograms of coating material, plus the time and energy required to process material that never reached the product. You should only need to empty the dust col- lector monthly, not daily, as some companies do. Another tipoff that you're not running efficiently: Material covers the coater's walls and spray arms, which should never occur in a modern spraying system when set up correctly. In fact, you should not even need to clean the coater between every batch if you're coating the same product. Ideally, you'd only need to clean after every 15 batches or so. If the task takes 2 hours, you can save a lot of time and money by reducing how frequently you clean. Whatever the interval, always follow GMP requirements. In a coating process that uses modern equipment, at least 95 percent of the coating solids should remain on the tablets. If you maintain the coater well and set the parameters correctly, it's even possible to achieve 100 percent solids usage. Common sources of inefficiency include turbulence, incorrect bed temperature, and poor spray gun setup. Turbulence In efficient coaters, process air flows in and out of the drum smoothly and consistently. In inefficient opera- tions, there's turbulence, usually because the inlet and exhaust volumes are imbalanced. That causes solids to deposit where they shouldn't, as shown above. To correct that, set the inlet air volume according to the weight of the product in the coater and set the exhaust air volume so that it creates a negative pressure within the housing, around 100 pascals. That should ensure the air entering the coater is removed by stream- lined air flow through the tablet bed. When the inlet air volume is excessive, it creates turbulence in the coater, causing the coating solution to spray-dry and allowing the solids to deposit elsewhere. When practiced cor- rectly, film coating is a very clean process and there is no reason for coating material to deposit on the coater's door or spray arm. For some reason, many companies tol- erate it or deem it acceptable. Turbulence can occur when the inlet and exhaust volumes of process air are out of balance. As a result, solids deposit where they shouldn't, including the coater door and drum end.