Conte U, Maggi L
Department of Pharmaceutical Chemistry, University of Pavia, Italy.
Biomaterials. 1996 May;17(9):889-96. doi: 10.1016/0142-9612(96)83284-4.
A new multi-layer tablet design has recently been proposed for constant drug release: Geomatrix Technology (Jago Pharma, Muttenz, Switzerland). It consists in the application of a drug-free barrier layer on one or both bases of an active core (hydrophilic matrix). The partial coating modulates the core hydration process and reduces the surface area available for drug release. The result is an extended release that draws close to a linear profile. The device was mainly intended for soluble drugs, while an excessive reduction of the release rate may be obtained with drugs of low solubility. In this study a new time-dependent polymeric barrier is proposed to control the release of sparingly soluble drugs. Two different barrier compositions (one swellable and one erodible) are applied on active cores containing drugs of different water solubility, Trapidil, Ketoprofen and Nicardipine hydrochlorides, and the drug dissolution patterns of the different multi-layer devices are compared. During dissolution, the swellable barrier swells and gels, but is not eroded, thus acting as a modulating membrane during the release process. The erodible barrier, instead, is progressively removed by the dissolution medium, exposing in time an increasing extent of the planar surface(s) of the core to interaction with the outer environment and to drug release. Both types of coatings are able to control drug release from the devices: the swellable barrier shows a stronger modulation efficiency and is more suitable to modify the delivery pattern of highly soluble drugs; the erodible barrier shows a time-dependent coating effect that provides better control of the dissolution profile of sparingly soluble drugs.
Geomatrix技术（瑞士米滕茨的Jago制药公司）。它包括在活性核心（亲水性基质）的一个或两个基底上应用无药阻挡层。部分包衣可调节核心的水合过程，并减少可用于药物释放的表面积。结果是实现了接近线性分布的缓释。该装置主要用于可溶性药物，而对于低溶解度药物可能会过度降低释放速率。在本研究中，提出了一种新型的随时间变化的聚合物屏障来控制难溶性药物的释放。将两种不同的屏障组合物（一种可溶胀的和一种可侵蚀的）应用于含有不同水溶性药物（曲匹地尔、酮洛芬和盐酸尼卡地平）的活性核心上，并比较不同多层装置的药物溶解模式。在溶解过程中，可溶胀屏障会溶胀并形成凝胶，但不会被侵蚀，因此在释放过程中起到调节膜的作用。相反，可侵蚀屏障会被溶解介质逐渐去除，随着时间的推移，核心的平面表面与外部环境相互作用并进行药物释放的面积会越来越大。两种类型的包衣都能够控制药物从装置中的释放：可溶胀屏障显示出更强的调节效率，更适合改变高溶性药物的释放模式；可侵蚀屏障显示出随时间变化的包衣效果，能更好地控制难溶性药物的溶解曲线。
