Design and evaluation of pH-independent pulsatile release pellets containing isosorbide-5-mononitrate.

A three-layered, pH-independent pulsatile release pellets system containing isosorbide-5-mononitrate (ISMN) was studied. The process of the heart disease such as angina has a close relationship to the chronobiology, which gives rise to the need of a pulsatile drug deliver system for the anti-anginal drug. In this study, pellets containing ISMN were firstly prepared as the core, and then layered with a swelling layer followed by an water-insoluble control layer. The core pellets were formulated with microcrystalline cellulose (MCC) and lactose, and were prepared by extrusion-spheronization. The preparation was optimized by Box–Behnken experimental design, when taking the MCC/lactose ratio as swell as the operating conditions of extrusion-spheronization as variables. The experimental results demonstrated the relationships between formulation, operation and properties of the product, and meanwhile provided optimized values for the parameters. The core pellets were coated by a fluidized bed coater, and pellets with various coating types and coating levels were studied by in vitro dissolution tests. The effects of both swelling layer and control layer on the lag time and the drug release time were studied, in order to predetermine the lag time and release time. The pellets were also evaluated in vivo by studying the pharmacokinetics after oral administration in beagle dogs. The pellets achieved a lag time of 4.1 h in vivo, which had a good consistency with the in vitro results, and the relative bioavailability was nearly 100% comparing to the normal tablets.