title: Preparation of theophylline hydrogels of atactic poly(vinyl alcohol)/NaCl/H2O system for drug delivery system.
abstract: Theophylline (TH) was loaded in an a-PVA/NaCl/H2O hydrogels system by one cycle gelation only at -20 degrees C. However, it developed some unwanted crystal-like structure surrounding the hydrogels while kept at room temperature. The physical, chemical and thermal analyses of this crystal-like structure indicated TH embedded with thin hydrogels of a-PVA/NaCl. Later during dissolving of feed-mixture at least 3 h heat treatment with proper mixing at high temperature contributed hydrogels of almost no crystal-like structure. 3% of TH was successfully loaded by this way. This type of hydrogels showed Fickian type drug release (Higuchi Model) and it showed a more sustained effect than that of traditional cyclic FT. Comparatively lower release rate, diffusion coefficient and kinetic constant values of this system prevail over other systems studied here. A DSC thermogram revealed that apparently homogeneous microgel junctions might play the key role behind the above properties. Moreover the a-PVA/TH/NaCl/H2O system depresses the freezing point at -30 degrees C instead of above this temperature. The hydrogels of this system were also prepared by freezing at -30 degrees C for 16 h as one cycle. Three cycles were done in cyclic FT (freezing at -30 degrees C for 16 h and thawing at room temperature for 8 h). Drug release was studied for a total of 750 min. Up to the asymptotic value, 10.5 h TH release from the hydrogel matrices of the a-PVA/NaCl/H2O system (gelation at -20 degrees C) and 6.5 h from those of a-PVA/NaCl/H2O (freezing at -30 degrees C) and a-PVA/H2O systems (cyclic FT) were found.
authors.affiliation: Faculty of Textile Science and Technology, Ueda City, Tokida 3-15-1, Nagano, Japan.
authors.forename: Sharif M
authors.initials: SM
authors.lastname: Shaheen
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamaura
mesh_terms: D002152:Calorimetry, Differential Scanning; D003692:Delayed-Action Preparations / Q000737:chemistry; D004339:Drug Compounding; D020100:Hydrogels / Q000737:chemistry; D007700:Kinetics; D011142:Polyvinyl Alcohol / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry; D013696:Temperature; D013806:Theophylline / Q000737:chemistry*; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D003692:Delayed-Action Preparations; D020100:Hydrogels; D014867:Water; D012965:Sodium Chloride; D011142:Polyvinyl Alcohol; D013806:Theophylline