Generally, since at least 6 months are usually needed for accelerated testing of tablet at 40 °C/75% relative humidity (RH), it would be crucial important to predict the dissolution profiles during long-term storage period by using samples stored with shorter periods such as 3 months. In this study, we developed a new method for predicting changes in dissolution from tablets during long-term storage-based changes in the available surface area [S (t)]. In addition, we discussed the dissolution behavior and mechanisms using S (t). The results revealed drastic delays in dissolution in samples stored at 40 °C/75% RH for 7 weeks. Considering changes of S (t) patterns, this delay was derived from changes of the tablet surface. New parameters, namely T22.1 and T63.2, calculated from the S (t) profile tended to increase with an increased duration of testing. Concerning the long-term prediction model using short-term data, a nonlinear model was deemed appropriate because good agreement was observed between the value predicted using the model and the measured value for samples stored at 40 °C/75% RH for 6 months. Therefore, using the new evaluation method based on S (t), we can predict changes in dissolution during long-term storage using short-term methods.
Keywords: Available surface area Dissolution model Long-term stability Solid dosage form