Development of oral controlled release preparations, a PVA swelling controlled release system (SCRS). II. In vitro...

A novel controlled release system, the PVA swelling controlled release system, was evaluated in vitro and in vivo using emedastine difumarate as a model drug. In the in vitro drug release study, the release profile of this system had almost zero-order kinetics. The effect of dissolution test conditions, which were paddle rotation speed, mechanical stress, and pH of the dissolution medium, on the release rate was very small. In an in vivo human bioavailability study of two formulations with a different release rate, the absorption rate was dependent on the release rate, and both formulations showed constant plasma levels of the drug for long periods. The variations of plasma concentration on the simulation of repetitive administration of the formulations at 24-h intervals were almost equal to the experimental value for the twice daily controlled release capsule currently on the market. It is concluded that the PVA swelling controlled release system is feasible for a long-acting preparation as a once-daily treatment.