Hydrogels, composed of poly(acrylamide-co-maleic acid) were synthesized and the release of vitamin B 2 from these gels was studied as a function of the pH of the external media, the initial amount of the drug loaded, and the crosslinking ratio in the polymer matrix. The gels containing 3.8 mg of the drug per gram gel exhibit almost zero-order release behavior in the external media of pH 7.4 over the time interval of more than their half-life period (t 1/2 ). The amount of the drug loaded into the hydrogel also affected the dynamic release of the encapsulated drug. As expected, the gels showed a complete swelling-dependent mechanism, which was further supported by the similar morphology of the swelling and release profiles of the drug-loaded sample. The hydrophilic nature of the drug riboflavin does not contribute toward the zero-order release dynamics of the hydrogel system. On the other hand, the swelling osmotic pressure developed between the gels and the external phase, due to loading of the drug by equilibration of the gels in the alkaline drug solution, plays an effective role in governing the swelling and release profiles. Finally, the minimum release of the drug in the swelling media of pH 2.0 and the maximum release with zero-order kinetics in the medium of pH 7.4 suggest that the proposed drug-delivery devices have a significant potential to be used as an oral drug-delivery system for colon-specific delivery along the gastrointestinal (GI) tract.

No abstract