抄録
The degradation rate of active ingredient of drugs in homogeneous or heterogeneous system was found to conform to a rate equation within a range of degradation ratio. The equation was obtained by using a Weibull probability paper [numerical formula] where α is degradation ratio, t is time, and m and k are parameters. The rate equation was corresponded to usual reaction rate equations. As a result, it exhibits good approximation within the range of degradation ratio of 1-30%, and the Arrhenius equation can be applied to these parameters. In the present investigation, acetylsalicylic acid solution, ascorbic acid solution, ascorbic acid-mannitol powder, and pyridoxal phosphate solution were used to exemplify those points. As a result, the degradation ratio predicted was in good agreement with those observed. It may be concluded that a method by the Weibull probability paper suggested in the present paper is useful on account of its convenience and accuracy of the prediction compared with usual ones by reaction kinetics.
