Isosorbide mononitrate chronopharmacological sustained release pellet drug delivery system and its preparation method

The invention discloses an isosorbide mononitrate chronopharmacological sustained release pellet drug delivery system and its preparation method. The system which is a preparation adopts a coated pellet as a main preparation form, and a pellet core is prepared through mixing a drug-containing sustained release pellet, a diluent and a lubricant and compacting; and coating layers outside the pellet core sequentially comprise, from inside to outside, an isolation layer, an expansion layer and a controlled release layer. A time lag effect is commonly generated by coating layers made from different materials outside the pellet core, and the pellet is disintegrated to form sustained release pellets which are uniformly distributed in the digestive tract, so the irritation of the drug to the gastrointestinal tract is reduced, the biological utilization degree of the drug is improved, and the influence of the burst release or the delay release of individual pellets to the whole preparation release behavior is very small. The pellet is taken every night before bed, can provide an effective plasma concentration during the matinal high-attack period and the early-morning sudden-attach period of angina pectoris patients, and has the characteristics of less taking frequency, long drug effect lasting time, difficult generation of the drug resistance, and the like.