Determination of Particle Size and Its Distribution of Drug Powder by Dissolution Rate Measurements

概要

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It was confirmed that the particle size distributions could be effectively obtained by dissolution rate analysis. If the drug dissolves by a diffusion-controlled mechanism and the absorbance E of its solution obeys the Beer's law, the absorbance change with respect to time t will be proportional to the surface area S and be expressed as dE/dt=k'S, where k'is a constant. When a drug powder is composed of n uniform and spherical particles the following equation d^2E/dt^2=k'dS/dt=Kn (τ-t) will hold, where τ is the disappearance time of the particles and K is a constant. Any powder can be considered as a set of n_1,n_2‥‥particles having the diameter of D_1,D_2‥‥, and the equation can be transformed into d^2E/dt^2=K{n_1(τ_1-t)+n_2(τ_2-t)+n_3(τ_3-t)+‥‥}. Thus the size distribution of a powder on the number basis can be determined from the tangent on the d^2E/dt^2-time curve. The proposed method was applied to benzoic acid crystals and the results were compared with those from microscopic analysis, and the agreement was fairly good. The mechanical trituration effects on the sulfanilamide crystals were also studied by this procedure. Thus it was found that the method gave the effective diameter for dissolution and the results could be obtained in much shorter time as compared with the ordinary methods such as microscopic analysis.
公益社団法人日本薬学会の論文
1978-05-25