Swelling kinetics and release studies of theophylline and aminophylline from acrylic acid/n-alkyl methacrylate hydrogels

Swelling kinetics and drug release (theophylline and aminophylline) from ac rylic acid/n-alkyl methacrylate hydrogels are presented. Swelling rate of x erogels decreases as the alkyl chain length in the hydrogels increases beca use of the increasing hydrophobicity: however, the equilibrium swelling inc reases with increasing chain length. Drug release from swollen hydrogels is Fickian. Theophylline release is fairly independent of alkyl chain length whereas aminophylline release is highly dependent of alkyl chain length whi ch suggest steric effects and stronger affinity of the latter with the hydr ogels. Drug release from xerogels is also different for theophylline and am inophylline. The release of theophylline from xerogels is diffusion control led and so, it has only a small dependence on the viscoelastic relaxation o f the polymeric matrix. By contrast, release of aminophylline from xerogels is non-Fickian. (C) 2001 Elsevier Science Ltd, AH rights reserved.