Solution stability of ciclosidomine

The stability of N-cyclohexanecarbonyl-3-(4-morpholino)-sydnone imine hydrochloride (ciclosidomine) in solution was studied as a function of pH, temperature, ionic strength, and buffer species. The rate of hydrolysis in the absence of light was found to be apparent first order in drug and general acid- and base-catalyzed reactions. The pH rate profile at an ionic strength of 0.1 M at 60 degrees C had a minimum value near pH 6. Change in ionic strength in the range of 0.05 to 0.2 M did not affect the rate of degradation at pH 7 (carbonate buffer) or pH 2 (phosphate buffer) at 60 degrees C. Similar degradation rates were noticed in air or nitrogen in the dark at pH 3, 5, and 6. However, degradation in light was very rapid in either case at pH 3, 5, and 6, and, therefore, the protection of solutions from light was required during all studies. The time for 10% loss of drug in solution at pH 6 in dilute phosphate or citrate buffer at an ionic strength of 0.154 M was projected to be 9 months at 20 degrees C and 2.6 months at 30 degrees C.