SQUEEZING HYDROGELS FOR CONTROLLED ORAL-DRUG DELIVERY

A new delivery device based on a novel, squeezing hydrogel concept, ut ilizing specific swelling-deswelling characteristics of temperature-, temperature/pH- and pH-sensitive hydrogels is described. These hydroge ls have been designed to exhibit controlled swelling-deswelling kineti cs, hence, a variety of release profiles may be generated including: d elayed, zero-order or on-off release profiles. A temperature sensitive NiPAAm/AAc hydrogel demonstrated a squeezing controlled 'on-off' rele ase profile in response to a temperature change between 35 degrees and 40 degrees C with the 'on' phase at higher temperature. Drug release profiles from a pH/T sensitive NiPAAm/BMA/DEAEMA hydrogel were strongl y affected by a pH change at 37 degrees C. The gel demonstrated a mini mal delayed release at pH 2.0 and a zero-order release at pH 7.4 contr olled by mechanical squeezing mechanism that was determined by the gel deswelling kinetics. A delayed and a zero-order release profiles were also obtained for a pH sensitive cationic hydrogel in response to a p H change from pH 2.0 to 7.4. For all studied systems, it was concluded that a gel composition and an applied stimuli (T, pH, pH/T), determin ed the gel swelling/deswelling kinetics and the release profiles. (C) 1997 Elsevier Science B.V.