Document Detail

The evaluation of the rheological properties of lactose/microcrystalline cellulose and water mixtures by controlled stress rheometry and the relationship to the production of spherical pellets by extrusion/spheronization.
MedLine Citation:
PMID:  12356419     Owner:  NLM     Status:  MEDLINE    
The consistency of wet powder masses produced from two ratios (7:3 and 8:2) of alpha-lactose monohydrate (L) and microcrystalline cellulose (MCC) mixed with a range of water contents has been assessed with a parallel plate controlled stress rheometer. The range of water contents, which could be studied, was restricted to those, which could be extruded uniformly by a ram extruder. In the creep mode, the instantaneous compliance increased as the water content increased for both L:MCC ratios illustrating the increasing deformability of the mixtures with increasing water content. The derived apparent viscosity of the mixtures as a function of shear rate, increased as the water content decreased and the values for all the systems fell on a common line. This indicates that the measurements are providing a reliable assessment of the mixtures and that the change in water content and L:MCC ratio provides systems, whose change of viscosity with rate of shear is consistent at low rates of shear. The values of the storage and loss moduli obtained from oscillatory measurements, increased with a decrease in water content but this time the two ratios of L:MCC were not on a common line when related to the water content of the mixtures. There was a range of water levels over which both the values of the storage and loss moduli were approximately constant. This corresponded to the level of water, which produced the pellets of the smallest diameter and range of diameters and were of the most spherical shape when produced by a ram extruder and spheronization. For 8:2 L:MCC ratio, there appeared to be a value for both the storage and the loss moduli above which the wet mass could not produce good pellets. For the 7:3 L:MCC these limiting levels were not achieved before extrusion with steady state conditions could be maintained without the mass being too wet or too dry. Instead, there appeared to be minimum levels of the moduli required to ensure that the mixtures were able to produce good pellets.
K A MacRitchie; J M Newton; R C Rowe
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Publication Detail:
Type:  Evaluation Studies; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences     Volume:  17     ISSN:  0928-0987     ISO Abbreviation:  Eur J Pharm Sci     Publication Date:  2002 Oct 
Date Detail:
Created Date:  2002-10-01     Completed Date:  2003-04-21     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9317982     Medline TA:  Eur J Pharm Sci     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  43-50     Citation Subset:  IM    
Copyright Information:
Copyright 2002 Elsevier Science B.V.
The School of Pharmacy, University of London, 29/39 Brunswick Square, London WC1N 1AX, UK.
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MeSH Terms
Cellulose / chemistry*
Chemistry, Pharmaceutical
Drug Implants
Lactose / chemistry*
Technology, Pharmaceutical
Water / chemistry*
Reg. No./Substance:
0/Drug Implants; 0/microcrystalline cellulose; 63-42-3/Lactose; 7732-18-5/Water; 9004-34-6/Cellulose

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