The drug concentration of the second drug layer is higher than the first layer, and therefore ascending release can be achieved through the drug concentration gra- dient.In the later stages of drug release, although the matrix erosion rate slowed, the majority of the matrix had dissolved, thus re- ducing the barrier and so the drug release rate was still increasing.compression-coated tablets include glipizide marketed tablets (Glucotrol XL, Pfizer of USA), nifedipine controlled release tablets (Adalat, Bayer of Germany), amoxicillin and potas- sium clavulanate compression-coated tablets (Moxicle TM,

Korea) and more.It has been used in the pharmaceutical field for many purposes, such as separating in- compatible drugs and combining drugs to achieve different therapeutic effects [10], protecting drugs with oxygen labile, acid-labile, light-sensitive or hygroscopic characteristics [11], for delayed release [12], pulsatile release [13], colon-specific release [14], programmable release, to modify pH sensitivity [15,16] and more.