Blends of hydrophobic and swelling agents in the swelling layer in the preparation of delayed-release pellets of a hydrophilic drug with low MW: Physicochemical characterizations and in-vivo evaluations

Abstract

In this study, a hydrophobic material, ethylcellulose, which was used as its aqueous suspension Surelease®, was combined with a swelling agent as the swelling layer to prepare delayed-release pellets for Danshensu, which is a hydrophilic drug with low MW. A rupturable, delayed-release pellet consists of a drug core, a swelling layer containing a swelling agent (cross-linked sodium carboxymethyl cellulose) with a hydrophobic agent (Surelease®), and a controlled layer composed by an insoluble, water-permeable polymeric coating (aqueous ethylcellulose dispersions) was developed in a fluidised bed. Results showed that blending Surelease® into the swelling layer could effectively extend the release of Danshensu from the pellets, which may be attributed to the slowed swelling rate by reduction of water penetration and improvement of mechanical integrity of the swelling layer. Drug in the delayed pellets showed sustained release in beagle dogs after oral administration with comparable in-vivo exposure to the uncoated drug pellets. In conclusion, blends of hydrophobic and swelling agents in the swelling layer in double-membrane pellets could achieve a delayed drug-release profile in vitro, as well as delayed and sustained absorption in vivo for highly soluble, low-MW drug. The present study highlighted the potential use of a delayed-release system for other hydrophilic, low-MW drugs to meet the formulation requirements for chronopharmacological diseases.