A novel hybrid solid dispersion film coat as a moisture barrier for pharmaceutical applications


In the present study, a novel hybrid moisture barrier film coat, based on a solid dispersion of a stearic acid (SA) in hydroxypropyl cellulose (HPC) using a polymeric surface active agent (PSAA), has been developed. The hybrid free films, prepared by a solution casting method, were characterized by water vapor transmission rate, DSC, mechanical tests, SEM and contact angle measurement to assess the structure-properties relationships of the films. The hybrid film formulations were then used to coat tablets containing CaCl2 as a moisture absorbing agent to study the coating and sealing properties of the films. The results have shown that a specific weight ratio between the components, could considerably increase the barrier capability of the film against moisture as compared to either pure HPC or the combination of HPC and SA, while keeping the basic properties of the HPC. This specific feature, could be attributed to the presence of PSAA in the film, which may form micelle-like structures entrapping the SA, to result in a reduced interfacial tension and thus a tight integration between two opposing phases (HPC and SA). By this means the micro-sized SA particulates could be evenly dispersed within HPC matrix to obtain an efficient solid dispersion.