Dissolution profile for multisized drug particles: new approximate expression.

New approximate expressions for the weight fraction undissolved were obtained using the Taylor series expansion. These approximations were tested using simulated data for multisized drug particle populations. The resulting calculations show that: (a) the approximations are not dependent on a knowledge of the analytical form of the particle-size density function, (b) the distribution effects are accounted for, but only a knowledge of the sample mean and standard deviation is required, and (c) the approximations (especially on a weight basis) lead to values within the limits of error in dissolution studies, thus posing the question of whether published exact experessions have practical value.