[Comparative studies on the stability of aqueous drug solutions in the isothermal and the non-isothermal short-time test as well as in the long-time test. Part 2: The stability of aqueous tetracaine solutions in the non-isothermal short-time test (author's transl)].

A study of the hydrolytic degradation of tetracaine solutions at various pH values demonstrates that the results from non-isothermal stability testing with logarithmic rise in temperature are in good agreement with the activation energies determined, under analogous conditions, by means of the isothermal short-time test and long-time test. The range of the maximum of stability is more clearly evinced by the non-isothermal short-time test than by the isothermal stability test. The comparison of the two methods reveals that the deviation of the reaction rate constants is greater in the non-isothermal test, which is due to the calculation required for the logarithmic rise in temperature. The results obtained with tetracaine evidence that the non-isothermal stability test is an appropriate method for the rapid determination of stability parameters (e.g. stability maximum, hydrolysis velocities) in the frame-work of testing potential drugs for stability and in the optimization of prescriptions.