Dissolution of Solid Dosage Form. V. New Form Equations for the Non-sink Dissolution of a Monodisperse System.

Abstract

The derivation of equations available for the treatment of a dissolution process of a monodisperse system with an optional initial amount within solubility was attempted. Two kinds of dissolution equations were derived as a function of the initial amount used in the dissolution test by using MacLaurin's expansion. When the initial amount is equal to one-third of the solubility, a semilogarithm form dissolution equation was deduced as was abbreviated as the Ln-z equation. When the initial amount is an amount other than one-third of the solubility, the derived equation was expressed by a form which included the cube root law and negative two-thirds law equations, and was abbreviated as the z-law equation. Also, the Langmuir form dissolution equation was obtained as an extended application form of the z-law equation, and was abbreviated as the Lg-z equation.Since the applicability or validity of the z-law equation was examined in a previous paper, the applicabilities of the Ln-z equation and the Lg-z equation were examined in this paper. As a result, it was suggested that the dissolution rate constant of a substance can be determined by dissolution measurement with an optional initial amount, and once the dissolution rate constant is determined in advance, the dissolution process of the substance with any optional initial amount within solubility can be approximately predicted.