ABSTRACT
The main objective of this investigation was to describe the mechanismof drug release from Carbomer 934 hydrogel matrices and to evaluate the effect of polymer level, diluent type, and matrix restriction using customized device (that permits only one surface of the tablet to be exposed to the dissolution medium) on theophylline release from Carbomer matrices. Formulations containing theophylline (10 percent), Carbomer (10 percent, 30, 50 percent), direct compressible diluent (lactose fast flo, Avicel PH-101, Emcompress) and magnesium stearate (0.75 percent) were compressed at a target tablet weight of 450 mg and target hardness of 7-9 Kp. USP Apparatus 1, was used to test the drug release and Korsmeyer equation was used to describe the mechanism of drug release from Carbomer matrices. Results show that the release profile and release mechanism from Carbomer matrices were influenced by Carbomer level, diluent type, and matrix restriction. In general the release mechanism was anomalous (non-Fickian) except for 10 percent and 30 percent Carbomer level and in Avicel PH-101 matrices, where, the release mechanism appears to follow super case II where, the n exponent has value greater than 0.89. All formulations selected appear to follow zero order release only up to 120 minutes. Restriction of tablet surface resulted in a shift toward Fickian release. This study demonstrated that it is possible to modify the drug release mechanism and rate, by changing polymer level, diluent type, and imposing physical restriction on the surface of the matrix.