Preparation of sustained-release tablets using a solventless-mixing tablet coating technique: Particle design of dry ammonioalkyl methacrylate copolymer latex with high coating performance using sodium lauryl sulfate

The aim of this study was to produce sustained-release tablets by V-shaped blending of polymer and tablets without using solvents or heating, and we investigated the design of polymer particles with high coating per-formance by modifying the structure of the particles using sodium lauryl sulfate. Dry-latex particles of ammo-nioalkyl methacrylate copolymer were prepared by adding the surfactant into aqueous latex, followed by freeze drying. The resulting dry latex was mixed with tablets (1:10) using a blender and the resulting coated tablets were characterized. Tablet coating by the dry latex was promoted as the weight ratio of surfactant to polymer increased. At a surfactant ratio of 5%, deposition of the dry latex was most effective and the resulting coated tablets (annealed at 60 degrees C/75%RH for 6 h) exhibited sustained-release characteristics over a period of 2 h. The addition of SLS prevented coagulation of colloidal polymer in the freeze drying, resulting in a loose-structured dry latex. This latex was easily pulverized by V-shaped blending with tablets and the resulting fine particles with high adhesiveness were deposited on the tablets. However, at a surfactant ratio of 10%, the coating of dry latex decreased due to reduced adhesiveness.