INTERPRETATION OF PERCENT DISSOLVED-TIME PLOTS DERIVED FROM IN VITRO TESTING OF CONVENTIONAL TABLETS AND CAPSULES

It is shown that under sink conditions a percent dissolved value at time t may simply be equivalent to the percent surface area generated to time t. If this is so, then percent dissolved‐time data may best be described by a distribution function and the parameters of the distribution employed to describe the data. Simulated percent dissolved‐time data, generated by means of the logarithmic normal distribution function, are shown to yield apparent first‐order plots. Hence, if the new concept is correct, apparent first‐order kinetics, derived from in vitro dissolution tests on conventional tablets and capsules, may be an artifact in some cases. In the special case when surface area of drug available for dissolution decreases exponentially with time after some lag time, to, then first‐order kinetics appear applicable to the dissolution data. Relationships between many of the constants in formerly derived dissolution rate equations and some equations derived in this report are shown. Dimensions of the constants are clarified. The new method of dissolution rate data examination is capable of providing characterizing parameters of greater potential utility than conventional treatments heretofore used. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company