The pharmaceutical characteristics of Theodur (TD), Theolong (TL) and Slo-bid (SB) as commercial theophylline sustained-release preparations were investigated. According to the experimental design under the conditions consisted of temperature (20-80°C) and relative humidity (40-80%), these preparations were kept under five kinds of storage conditions for 14 days. The contents of theophylline in each of the preparations were stable. When preparations were kept at 80°-70%, the hardness of TD reduced rapidly with the passage of time. After keeping the preparation in 80° for 14 days, the release of theophylline from TD was accelerated. On the other hand, release of theophylline from TL was delayed with increasing temperature. SB was not suffered from temperature and relative humidity on the release of theophylline.
In the cases of TD and TL, the effect of the structural change on the release profiles was suggested by surface condition observation using a scanning electron microscope. Response variables were predicted by multiple regression analysis and simulation technique. The results reveald that each sustained release preparation designed by our pharmaceutical technique have different characteristics and produced a different effect on the drug release profiles according to the storage conditions.