Enteric coating of soft gelatin capsules by spouted bed: effect of operating conditions on coating efficiency and on product quality

The present study was conducted in order to analyze the viability of the spouted bed process for application of a gastric-resistant coating to soft gelatin capsules. The variables investigated were: included angle of conical base, (gamma), the relation between the feed mass flow rate of the coating suspension and the feed mass flow rate of spouting gas (W-s/W-g); the ratio between the flow rate of the spouting gas and the flow rate at minimum spouting condition (Q/Q(ms)); the mass of capsules in the bed (M-0), and the capsule's size. The product quality was measured by disintegration tests, traction X deformation tests, image analysis and by the evaluation of the coating mass distribution and shape factor variation during the coating operation. The experiments were performed in a spouted bed with a column diameter of 200 mm and included a conical base angle of 40degrees. The best coating efficiency values were obtained for M-0 = 300 g. Coating efficiency tended to increase with increasing W-s/W-g ratio. Disintegration tests showed that the gastric-resistant effect was obtained with a coating mass of 3.86 mg/cm(2). The shape factor increase during the coating operation. The capsule's coating mass distribution tended to maintain the original distribution. (C) 2003 Elsevier Science B.V. All rights reserved.