When Hydrophilic polymer substance dissolve in water it starts to hydrate and forms a gel matrix from which drug could be released at a controlled speed or in a preferred internal position. Hydrophilic polymer tablets generate several gel layers in the swelling process, in the erosion layer all the drug releases to the dissolution medium; in the swelling layer drug releases through apertures in the gel matrix. The interfaces between these layers are called swelling front and erosion front. Observing the location shift of swelling front and erosion front could disclose the mechanism refers to the tablets swelling and releasing behaviors. This review briefly discusses the basic principles and progress of commonlyobserving methods-namely gravimetric method, image analysis method, magnetic resonance imaging (MRI), and ultrasound techniqus-that currently applied to the tablets swelling study.%亲水性聚合物如羟丙基甲基纤维素(HMPC)等物质在溶出介质中会发生水化作用,膨胀生成网状凝胶,常加入口服药片中以制成控缓释制剂,起到调节药物释放速度及其在体内释放位置的作用.亲水聚合物在膨胀的过程中形成数层凝胶层,在药片被侵蚀的部分,所含有的药物均被释放,而在药片的膨胀部分,药物经由凝胶网状空隙溶解释放,这些不同的凝胶层由膨胀边缘和侵蚀边缘作为分界面,因此研究药片溶出时膨胀边缘和侵蚀边缘两层边界的位置可以揭示出药片膨胀和药物释放的机制,是控缓释制剂新药研究的热点之一.本文就常用的研究方法,重量法、光学图像观察法、核磁共振成像法和超声波法等进行了阐述.
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