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 acrylic acid/n-alkyl methacrylate hydrogels are presented. Swelling rate of xerogels decreases as the alkyl chain length in the hydrogels increases because of the increasing hydrophobicity; however, the equilibrium swelling increases 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 which suggest steric effects and stronger affinity of the latter with the hydrogels. Drug release from xerogels is also different for theophylline and aminophylline. The release of theophylline from xerogels is diffusion controlled and so, it has only a small dependence on the viscoelastic relaxation of the polymeric matrix. By contrast, release of aminophylline from xerogels is non-Fickian.