DRUG RELEASE FROM WAX MATRICES .2. APPLICATION OF A MIXTURE THEORY TO SULFANILAMIDE-WAX SYSTEM

Using the T. Higuchi relationship for the release of a drug from a solid matrix, a hydrogenated castor oil—propylene glycol monostearate—sulfanilamide system has been investigated. Plots of the amount of drug released per unit of tablet surface area exposed as a function of the square root of time enabled comparison of the release for various concentrations of drug, and the calculation of the apparent tortuosity values. A model based on the Bruggeman mixture relationship for a two‐phase system has been used and equations were derived for the prediction of theoretical tortuosity values as a function of porosity due to drug. These theoretical values for tortuosity appear to follow a skewed convex parabolic function. The experimental results obtained compared well with the theoretical predictions. Copyright © 1968 Wiley‐Liss, Inc., A Wiley Company