Hydrogels for colon-specific oral drug delivery: An in vitro drug release study (II)

Drug-loaded cylindrical polymer matrices, composed of poly(N-vinyl-2-pyrrolidone) and poly(acrylamide-co-maleic acid) have been synthesized and the release of vitamin B-2 from these gels has been studied at the physiological temperature 37 degreesC. The devices show strong pH-dependent release behaveiour, thus offering a maximum release at pH 7.4. The initial amount-of drug loaded into the device and the diameter of the cylindrical samples also affect the release kinetics. With the increase in the maleic; acid content inside the device having maximum 43.0 mM, the release rate has been found to increase, whereas further increase in the acid content slows down the release rate. Finally, the release of riboflavin from the devices has been explained on the basis of the swelling-dependent mechanism.