Analysis of drug release behavior from swellable polymer carriers using the dimensionality index

The mode of expansion of swelling-controlled release systems may be used as an indication of the type of drug release behavior of such systems. This swelling phenomenon may be analyzed by defining and calculating the dimensionality index, d, a characteristic number which may be determined from a logarithmic plot of the swelling ratio of the carrier or system versus time. Various dimensionality indices may be determined by preparing hydrophilic discs or tablets and covering one or more of their sides with an impermeable coating. They can be correlated with the release rate and fractional drug released.