This paper deals with the application of rigorous stability analysis and predict time for degradation of solid pharmaceutical formulations. The stability analysis in the form of the tangent-plane criterion is used to predict the stability of certain solid formulations. The Michelsen vector which indicates instability when the sum of its components is greater than unity is differentiated with respect to time and the results are used to predict when instability sets in. The total degradation time is the sum of the time for instability to set in and the time for the mole fraction to reach a certain value.