Abstract: AimTo prepare terbutaline sulphate (TB) bi-layered pulsatile release tablets, evaluate the effects of the formulation and dissolution medium on drug release behavior, and to elucidate the mechanism of drug release based on obtained results. MethodsCore tablets containing osmotic active agent were prepared by direct compression and spray coated with swelling layer and semipermeable membrane subsequently. Pharmaceutical properties of TB pulsatile tablets were investigated by dissolution test. The water uptake kinetics and swelling behavior of tablet were studied by the water uptake test and project enlargement method. ResultsTB released from bi-layered tablets in pulsatile behaviors. The lag-time was prolonged with the increase of coating level of semipermeable membrane and the steady release rate was increased significantly with the increase of osmotic active agent and swelling layer. It was shown that drug release behaviors were constant irrespective of various pH of dissolution medium and rotation speeds. All results indicated that diffusion, swelling and osmotic pumping were involved in the mechanism of drug release. ConclusionIdeal pulsed release behaviors can be achieved by adjusting the coating level and composition of semipermeable membrane to meet the requirement of chronotherapy.