Compressibiliy and compactibility of pectin powders -A study of their potential as direct compression excipients in tablets

Abstract

Pektinpulver med ulike prosentar metoksylering vart komprimert i ein komprimeringssimulator. Dette er ei avansert tablettmaskin som svært nøyaktig måler distansen tablettstempelet har gått (på mikrometernivå) og kor stor kraft som er involvert under komprimeringa (samantrykkinga av pulveret). Pektin med metoksyleringsgrad under 10% (også kalla pektinsyrer) gav dei mekanisk sterkaste tablettane, og er såleis den pektintypen det bør fokuserast på i framtidige forsøk med pektin som eit tabletthjelpestoff. Høgmetoksylert pektin, dvs. meir enn 50% metoksylering, var ueigna i tablttering ettersom dei ikkje gav samanhengande tablettar. Hovudsakleg skjedde det ein elastisk deformasjon med pektinpartiklane, og sidan dette generelt er ugunstig med hensyn på binding og mekanisk sterke tablettar vart det undersøkt kva mekanismar som bidreg til at tablettane heng saman. Det vart funne at ei viss grad av fragmentering skjedde i pektinsyrene. Plastisk deformasjon var det lite av. Avhandlinga viser at pektinsyrene og til dels andre pektintypar med metoksylering mindre enn eller lik 40% er veleigna som eit tabletthjelpestoff som kan fungere som ein bærar av ein aktiv substans til tjukktarmen.

This thesis is dedicated to direct compression studies of pectin, a natural polysaccharide with potential as a pharmaceutical excipient due to its ability to act as a carrier for colon-specific drug delivery as well as for sustained drug release purposes. The main objective of this thesis was to study the suitability of pectin as a matrix former in tablets. The compressibility and compactibility of pectin powders were studied as a function of various degree of methoxylation (DM) grades and different particle sizes.

Pectin powders with similar powder characteristics were compressed by direct compression on a compaction simulator and an instrumented tablet press, respectively. The results showed that pectin powders, irrespective of DM and particle size, were classified as class IIA powders, showing a low degree of particle rearrangement and a relatively low degree of fragmentation. The powders were relatively soft and resembled the deformation behaviour of pregelatinized starch, an elastically deforming material. The pectinic acids (DM ≤ 10%) were slightly more viscoelastic than the other pectin grades. However, in general terms, it should be emphasized that the DM had a limited effect on the compression behaviour (i.e. compressibility) although an increased DM gave slightly softer and slightly less brittle particles. On the contrary, the compactibility was strongly dependent on both DM and initial particle size. The low-methoxylated (LM) pectin (DM < 50%) and especially pectinic acids (DM ≤ 10%) produced mechanically strong tablets, whereas the high-methoxylated (HM) pectins did not produce coherent tablets. The tensile strength increased with decreasing initial particle size. Pectin also proved to have a high dilution potential as a binder/matrix former, as coherent tablets were produced even when 70% of an inert material was incorporated. To summarize, the results showed that pectins with DM ≤ 40% have potential as direct compression excipients in tablets.