The invention relates to the technical field of medicines, in particular to a sustained-release
coating as well as a preparation method and application thereof. The
coating adopts a three-layer gradient structure design and comprises an inner layer
coating, a middle layer coating and an outer layer coating, and the
layers are compounded and matched through
ethyl cellulose and hydroxypropyl methylcellulose with different molecular weights and are combined with talcum
powder filling amount with gradient decreasing and a
triethyl citrate plasticizer, so that accurate regulation and control of
drug release are realized. Through hierarchical swelling-
diffusion dynamic balance, burst release is inhibited, the inner layer has high talcum
powder content to
resist initial swelling stress, the outer layer has low filling amount to maintain hydrophobic continuity, interface defects are reduced in combination with high-temperature curing, and the release stability and long-term storage performance of drugs such as dihydroergoline
mesylate are remarkably improved; the problems of sudden release, damp-
heat sensitivity,
impurity generation and the like of a traditional single-layer coating are solved.