Preparation and Characteristics of a Novel Sustained and Controlled Release Drug Delivery Device by Plasma Technique

Introduction

Increased complications and expense involved in marketing of new drug entities has focused greater attention on development of sustained and controlled release drug delivery systems [1]. The purpose of the systems is to maintain drug concentration in the blood or in target tissues at a desired value as long as possible. To achieve predictable and reproducible release rates, extended duration of activity for short half-life drugs, decreased toxicity, and reduction of required dose, optimized therapy and better patient compliance, a sustained-release (SR) formulation of various drugs is desirable [2].

Over the years, we have been working on the development of plasma-assisted preparation of multi-layered tablets applicable to oral drug delivery system (DDS) [3-5]. In previous papers, we reported the preparation of SR system by oxygen plasma-irradiation to the double- compressed tablet having a mixture of plasma- crosslinkabe material, like polystyrene (PSt) or hydroxypropyl methylcellulose acetate succinate (HPMCAS), and plasma-degradable material, like polyoxymethylene (POM) or lactose, as a wall material [6,7]. When oxygen plasma was irradiated to the outermost layer of the tablet, plasma-degradable material could be selectively eliminated and simultaneously plasma-cross-linkable material undergoes the rapid crosslink reaction to result in the formation of the porous outer layer of the tablet. As a result, the drugs could be released slowly from the tablet through the resulting micropores.

The objective of this study was to develop once-daily sustained-release dosage forms, which releases drug at zero-order rate with accurate control in the gastrointestinal tract.