Acrylic Latices from Redispersable Powders for Peroral and Transdermal Drug Formulations

Abstract

Aqueous dispersions of acrylic resins may be converted to pow ders by spray or freeze drying. Such solids contain loose ag glomerates of discrete latex particles, that disintegrate easily into the original latex particles of less than 2 µ;m in diameter. No film formation occurs, provided that the minimum film forming temperature of the latex is not exceeded during drying. Such powders can be redispersed in water in the presence of 3-6 mol% of alkali or organic bases to obtain a stable latex system. This can be used for enteric film coating in the same way as the original latex dispersions. Redispersed methacrylic acid copolymers can be mixed with neu tral, permeable emulsion polymers to adapt the release profile of drugs more specifically to match their pharmacokinetic prop erties. In this way the pH-dependent solubility of methacryic acid copolymers, which controls the release in the gut by dissolution or increasing permeability can be combined with the pH–independent permeability of neutral acrylic ester polymers, to give time controlled retardation. Similar formulations of acrylic resins can also be used to solve several problems of transdermal delivery systems. The described redispersable polymer powders are stable under normal storage conditions, so their handling and use as redispersed aqueous coating formulations is much more easier and will open an extended field of application.