Stability of trimedoxime in concentrated acidic injectable solutions

The degradation of trimedoxime in concentrated (114 mg/ml) acidic solutions was studied at several temperatures in the pH range 3.0 to 4.3. The degradation profile showed a relationship indicative of first-order kinetics. Trimedoxime was found to be stable in the pH range 3.0 to 3.8, with maximum stability at pH 3.0. The activation energy of the hydrolysis reaction at pH 3.0 was found to be 19.4 kcal/mol, and the half-life was 124 years. General equations were derived relating the half-life of trimedoxime solution to pH and temperature. The t90 value at 25 degrees C was calculated for each pH value studied and was found to be 11 to 18 years within the pH range 3.0 to 3.8.