非溶蚀型药物体系的释放动力学新模型──Fick第一扩散定律的修正及其应用

基于以下两点事实:Fick第一扩散定律中的扩散系数并非严格的常数,它随浓度变化;Fick第一扩散定律只适用于浓度梯度恒定的稳定扩散,而许多实验表明浓度梯度也是一个时间函数,本文对Fick第一扩散定律作出两点修正将原定律中浓度梯度和扩散系数分别修正为时间函数和浓度函数,从而导出关于非溶蚀型药物体系的释放动力学模型。该模型较其他常用释放模型有更好的拟合效果,其参数也有较为明确的物理意义。

A new dynamic model of release for not-corroded drug system--revision and use of Fick''s first law]

Based on the facts that the diffusion coefficient in original Fick's first law is not a strict constant but changes with concentration and that the original Fick's first law is only suitable for the stable diffusion with constant concentration gradient but many experiments have shown that the concentration gradient is a function of time. The authors suggest that the diffusion coefficient and the concentration gradient should be revised, respectively, as a concentration function and a time function. That is, [formula: see text] So, the Fick's first law is revised as [formula: see text] In the formula, dW/dt represents the rate of diffusion. D0 is the intrinsic diffusion coefficient that is a constant only concerning the temperature and the character of the substance diffused. A is the area of diffusion surface, alpha is the constant concerning the change of concentration gradient, C0 and C is, respectively, the concentration on the diffusion surface at time t0 and any time t. Based on this, the dynamic model of release on the preparations not-corroded is derived: [formula: see text] Here, k0 is the release constant concerning D0, temperature, C0 and A. The model gave better results than other models in common use for simulating the release dynamic process and the physical meanings of the model parameters are explicit.