Evaluation of low-substituted hydroxypropylcelluloses (L-HPCs) as filler-binders for direct compression

The aims of this study were to assess the potential value of low-substitute d hydroxypropylcelluloses (L-HPCs) as excipients of direct compression, and to investigate relationships between the chemical and physical properties of the polymers and (a) the powder rheological behavior and (b) drug releas e profiles from direct compressed tablets elaborated with (1:1) theophyllin e:L-HPC mixtures. Experiments were performed with five L-HPC varieties of d ifferent nominal particle sizes and degree of substitution. The products we re characterized with regard to the moisture content, density, IR and Raman spectroscopy, hydroxypropyloxy content, heat of hydration, particle size, specific surface and porosity, and important differences were found in rela tion with all these properties. The differences in specific surface princip ally determine the flow and compaction properties of the powders, and the m echanical and microstructural properties of the tablets. The control of the hydroxypropyloxy content and the particle size of the L-HPCs allow the the ophylline release profile to be regulated. (C) 2000 Elsevier Science B.V. A ll rights reserved.