The Manufacture and Characterization of Casein Films as Novel Tablet Coatings

The use of casein as a novel film-forming agent, capable of functioning as a pharmaceutical tablet coat, was assessed. Diltiazem HCl core tablets were coated with casein using a pan coater and the efficacy of four different plasticizing agents (glycerol, triethyl citrate, dibutyl sebacate and oleic acid) in producing a continuous tablet-coat were evaluated. Interestingly, only those films formed using oleic acid as a plasticizing agent were capable of producing a continuous, acceptable coat. Consequently, the drug dissolution properties of casein/oleic acid film-coated tablets in pH 1.2 and pH 6.8 media were further investigated. Post-coating thermal treatment (60, 80 and 100°C) was shown to have a significant effect on the properties of the casein-oleic acid films. Diltiazem HCl drug release at pH 1.2 was found to decrease with increasing post-coating heat treatment temperature. Additionally, only coated tablets that were subjected to post-coating heat treatment at 100°C showed sustained drug release properties at pH 6.8, which may be attributed to casein cross-linking.