The present invention is directed to immediate release film coating systems for use on oral dosage forms such as compressed tablets and other orally-ingestible substrates which have improved moisture barrier properties. The film coating systems can be applied either directly to a substrate or after the substrate has been coated with a subcoat. In preferred aspects the moisture barrier film coating is prepared as a dry powder mixture containing polyvinyl alcohol a polymer with pH dependent solubility a plasticizer a glidant and optionally a detackifier an alkalizing agent and a pigment. Film coating compositions containing an aqueous suspension of the powder mixtures methods of applying the coatings to substrates and the coated substrates are also disclosed.
