Characterization of monolithic matrix patch system containing tulobuterol

The aim of this study was to investigate the effect of the functional groups in acrylic adhesive on tulobuterol uptake, release rate and permeation rate across rat dorsal skin. In addition, the relationship between these parameters was identified in order to formulate the monolithic matrix patch system. Seven acrylate pressure sensitive adhesives were used in this study with three different functional groups as follows: (1) no functionality (DT-4098), (2) hydroxyl group (DT-2287, DT-2510, DT-2525, DT-2516), and (3) carboxyl group (DT-2353, DT-2852). Tulobuterol-uptake in PSA was determined by the drug-uptake method. The amount of tulobuterol-uptake in acrylic polymers with a carboxyl group was higher than those in acrylate pressure sensitive adhesives with either a hydroxyl group or a nonfunctional group. The release rate of tulobuterol from the monolithic patches was evaluated and DT-2353 and DT-2852, which contained a carboxyl group, showed lower release rates of tulobuterol than the other acrylate pressure sensitive adhesives. The skin permeation of tulobuterol was investigated using excised rat dorsal skin and the permeation rate of tulobuterol from DT-2353 and DT-2852 was also lower than the other acrylate pressure sensitive adhesives. Taking into consideration the relationship between all the parameters, pressure sensitive adhesives can be categorized into two groups: those containing a carboxylic acid functional group and those containing a non-carboxylic group. These results indicate that there was an interaction between the secondary amino group of tulobuterol and the carboxyl group of the acrylate polymer. Therefore, we suggest that a drug's chemical structure and functional groups in pressure sensitive adhesives must be considered in order to formulate a transdermal patch system.