El-Fattah S A, Daabis N A
Pharmazie. 1977 Apr;32(4):232-4.
The effect of dihydroxypropyl theophylline on the solubility and stability of menadione was investigated. An increase of about 4-fold in the solubility of menadione with 0.1 m dihydroxypropyl theophylline was observed at 30 degrees C. Thermodynamic paremeters were calculated by conducting the experiments at different temperatures. The rate of base-catalyzed degradation of menadione in the presence and absence of dihydroxypropyl theophylline was found to be first order with respect to the vitamin at all conditions of pH, temperature and concentration. Dihydroxypropyl theophylline leads to an accelerated rate of decomposition of the drug at relatively high pH values. This adverse effect decreases considerably as the pH of the solution approaches neutrality. At pH = 7.5, dihydroxypropyl theophylline exerts a rather stabilizing effect on menadione solution. The enhancement of the rate of base-catalyzed degradation is directly proportional to the concentration of dehydroxypropyl theophylline at pH = 9.2. The base-catalyzed degradation of menadione in the absence and presence of dihydroxypropyl theophylline follows Arrhenius' equation for the thermal activation of molecules. No noticeable variation in the energy of activation of both systems was detected. The addition of 4% dihydroxypropyl theophylline to menadione solution nearly completely suppressed the aerobic photodegradation of menadione.
研究了二羟丙基茶碱对甲萘醌溶解度和稳定性的影响。在30℃下，观察到0.1 m二羟丙基茶碱使甲萘醌的溶解度增加了约4倍。通过在不同温度下进行实验计算了热力学参数。发现在所有pH、温度和浓度条件下，有和没有二羟丙基茶碱时，甲萘醌碱催化降解速率对维生素而言均为一级反应。在相对较高的pH值下，二羟丙基茶碱会导致药物分解速率加快。随着溶液pH值接近中性，这种不利影响会显著降低。在pH = 7.5时，二羟丙基茶碱对甲萘醌溶液具有相当的稳定作用。在pH = 9.2时，碱催化降解速率的提高与二羟丙基茶碱的浓度成正比。有和没有二羟丙基茶碱时，甲萘醌的碱催化降解均遵循阿仑尼乌斯分子热活化方程。未检测到两个体系活化能有明显变化。向甲萘醌溶液中添加4%的二羟丙基茶碱几乎完全抑制了甲萘醌的需氧光降解。
