Suberin fatty acids isolated from outer birch bark improve moisture barrier properties of cellulose ether films intended for tablet coatings.
The purpose of the present study was to investigate an aqueous-based amylose-rich maize starch (Hylon VII) film-coating process of tablets performed by a side-vented pan coating system. Three formulation or process parameters of potential importance, including the plasticizer concentration (X(1)), the temperature of coating pan (X(2)) and the spray rate of the coating solution (X(3)), were evaluated using a central composite face-centred experimental design. Only a few process-related limitations associated with the aqueous film coating of Hylon VII were observed, and, in general, the coated tablets were of fairly good quality. At low spray rates, the temperature of the coating pan did not affect the roughness of the coated tablets. At higher spray rates, higher temperature gave smoother films. As regards surface quality and smoothness, a plasticizer concentration (i.e., a 1:1 mixture of sorbitol and glycerol) of approximately 65% of the polymer weight, seems to be suitable for the present formulations. The dissolution of all Hylon VII-coated tablets in an acidic medium was rapid, more than 75% of the drug (theophylline) dissolved within 15 min. On the basis of the present results, it can be concluded that amylose-rich maize starch (Hylon VII) may be considered as an aqueous film-coating agent to be used for pharmaceutical purposes and in established film-coating processes.