Novel pharmaceutical excipients

Abstract

The research work performed in compiling this thesis can be divided into two broad areas, namely (a) the development, characterisation and examination of potential pharmaceutical applications of new de-aggregated grades of microcrystalline cellulose (MCC) and (b) the characterisation and examination of potential pharmaceutical applications of a novel tubular clay mineral, termed halloysite. MCC is a white, free flowing, tasteless powder produced by the chemical partial depolymerisation of an a-cellulose rich wood pulp at elevated temperatures in the presence of mineral acid. Because of the variation in the raw material used and the conditions of manufacture applied, different grades of MCC are available, one of the principal brands being Avicel®, common grades of which are PH-101 and PH-102. In this project novel size reduced grades of MCC were developed. Preliminary size reduction studies on Avicel® PH-101 showed that chemical de¬aggregation using surfactants (a phenomenon observed by Law and Deasy, 1997) was less successful than mechemical methods. Ultrasonic homogenisation was most successful, resulting in a reduction in the average size of the Avicel® PH-101 grade to 10-15 nm. The effect of the production parameter, cycle number, on the mean particle size and the polydispersity index of the MCC suspensions was investigated. Size reduced MCC grades in combination with various de-aggregating agents were recovered using a spray-dryer.