Isothermal and nonisothermal kinetics in the stability prediction of vitamin A preparations.

A nonisothermal method was applied to shelf-life estimation of commercial vitamin A preparations. The usefulness and limitations of the nonisothermal method, as predicted by computer simulation, were validated. Degradation of vitamin A palmitate followed zero-order kinetics, and non-Arrhenius behavior was suggested for the rate constant. The nonisothermal method predicted a higher shelf-life value than the isothermal method for a syrup preparation, and vice versa, for an injection preparation. Analysis of the results suggested that the nonisothermal method provides better estimates of shelf lives than the isothermal method when drug degradation does not follow the Arrhenius equation near ambient conditions.