Swelling and Controlled Release of Tramadol Hydrochloride from a pH-Sensitive Hydrogel

Abstract

In the present study pH-sensitive polyvinylpyrrolidone/acrylic acid (PVP/AA) hydrogels were synthesized by free radical polymerization in the presence of ethylene glycol dimethacrylate (EGDMA) as a cross-linker. For this purpose, different concentrations of PVP, AA and EGDMA were used to synthesize polymeric networks. This study focused on evaluating the effect of the composition on the swelling of hydrogels and release of tramadol hydrochloride at varying pH (1.2, 5.5, 6.5 and 7.5). Gel fraction, porosity and diffusion coefficient were also determined. The hydrogels were characterized using scanning electron microscopy for surface morphology, Fourier transform infrared spectroscopy and X-ray diffraction for studying possible chemical interactions. The hydrogels exhibited a pH-dependent swelling behavior. The degree of swelling, as well as drug release from PVP/AA hydrogel, was significantly increased as pH varied from 1.2 to 7.5. Swelling was increased by increasing the AA content, while a decrease in swelling was observed with increasing EGDMA content. Drug-release data were fitted to kinetic models including zero-order, firstorder, Higuchi and Korsmeyer–Peppas. Results indicated that release of tramadol hydrochloride from the PVP/AA hydrogel was non-Fickian and that the mechanism was diffusion controlled.