METHODS OF IMMERSION COATING APPLICATION AND PROPERTIES OF CONTROLLED DIFFUSION PHARMACEUTICAL FILMS

The establishment and evaluation of variables involved in the process of immersion coating dosage forms was undertaken. The coating system used was a previously studied controlled diffusion film coating containing poly(methylvinyl ether/maleic anhydride) 169 copolymer (PVM/MA) crosslinked with Tween 20 and plasticized with triacetin in a ratio of 8 g/.56 ml/4 ml in ethyl acetate or mixtures of acetone and ethyl acetate as the solvent. An initial empirical analysis using immersion coating by hand was performed to isolate the process variables of immersion coating. This analysis revealed that angular entrance and exit of the dosage form into and out of the coating solution was essential. It also indicated that there was a velocity limit for emersion of the dosage form from the coating solution. An experimental immersion coater was constructed based on the analysis of process variables. This device was used to analyze machine/process variables. Using the same coating solution for coating studies involving the experimental coater it was found that a spinning motion (axial rotation) of the dosage form was required. It was also determined that a velocity of emersion of 172.5 inches per minute linear path speed avoided threading and air bubble entrapment. It also revealed that there was no stringent requirement for positioning the dosage forms relative to one another. In a separate study an evaluation of methods to accelerate the drying of the applied film coat was performed. It indicated that microwave drying was the most efficient method. However, due to lower cost and less operator hazard the second most efficient method; moving, heated air, was recommended as the method of choice. It was also found that mixed solvent systems composed of acetone and ethyl acetate provided more efficient drying than pure ethyl acetate. The mixed solvent was also found to cause more coating material to be applied upon each immersion. It was also evident from several studies that the concentration of polymer in the coating solution must be tightly controlled to reduce variability in the applied coat weight. During the course of the study a previously reported film system employed as a controlled diffusion membrane was found to be unreliable in actual in vivo use on coated dosage forms. . . . (Author\u27s abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UM