Theoretical Consideration on Dosage Variation

Even if a random distribution of particles has been achieved in the practical process, a precise quantity of an active ingredient in individual dose units can not be always assured. This variation in the potency is attributed to a problem of mixing and related directly to the sampling error. Theoretical consideration indicates that the variance in the proportion of an active ingredient developed through sampling from a randomized bulk mixture is calculated with the following equations ; 1. When the shape of particles is spherical [numerical formula] 2. When the shape of particles is cubic [numerical formula] where, P is the proportion of an active ingredient, g the sample weight, dA and dB are the the densities of components, LA and LB the mean volume diameters of components, σA and σB the standard deviations of particle-sizes distributions of components ; suffix A means the active component. The possible application of the result to suspension and emulsion has been discussed.