Coating uniformity and coating efficiency in a Bohle Lab-Coaterusing oval tablets

The aim of this study was the examination of the influence of tablet size (two different sized oval tablets), batch size, pan speed and inclination of the rotation axis on the coating uniformity and efficiency in a Bohle Lab-Coater BLC 5. The coating uniformity was appraised using the mass variance, the dissolved amount of acetaminophen after 2 h in hydrochloric acid pH 1.0 at a polymer loading of 3 mg/cm2 and the minimum amount of polymer for an enteric coating. The mass variance of the final tablets decreased with increasing pan speed. There was a linear and quadratic effect in the case of small oval tablets and a linear effect for the large tablets. The minimum amount of polymer required for gastric resistance depends on the pan speed for both tablet sizes. The dissolved amount of acetaminophen after 2 h in simulated gastric fluid was influenced linearly by the batch size for both kind of tablets. In the case of the large oval tablets it was also influenced by the pan speed, the batch size and the inclination of the rotation axis. The dissolved amount of acetaminophen increased with increasing pan speed and batch size. A relation between the coating process efficiency and the investigated influence variables could not be established.