MORPHOLOGICAL, PACKING, FLOW AND TABLETING PROPERTIES OF NEW AVICEL TYPES

The six Avicel products designed for compression - the classical grade s PH-105, PH-103, PH-101 and PH-102, and the new Avicels PH-112 and PH -200 - have been submitted to a comparative investigation for both the ir basic and tableting properties. According to the manufacturer all t hese products differ by their nominal particle size and moisture conte nt. Basic properties of the powders were first determined, namely mois ture content (loss on drying and Karl Fischer titration), particle siz e and shape (sieving and image analysis), densities (true bulk and tap densities, Hausner ratio) and flow properties (vibratory hopper techn ique). As tableting properties, the compactibility of the powders and the effect of adding a hydrophobic lubricant (0.5% magnesium stearate) on the compact strength were evaluated by preparing compacts at a giv en applied pressure using a hydraulic press. Weight and dimensional va riations were assessed by preparing tablets at a target crushing stren gth of 70 Newtons on a high speed machine. The comparison of the conve ntional Avicel PH grades showed that Avicel PH-105 differed markedly i n its properties (high compressibility on tapping, high compactibility , inacceptable tablet weight variability and very poor disintegrating properties) from the other grades. As to the two new Avicel PH grades, conflicting results with the literature were obtained with the low-mo isture product Avicel PH-112. We observed, like other authors but in c ontrast to manufacturer's data, values of compactibility and strength reduction ratio upon lubrication as well as of the coefficient of tabl et weight variation similar to those of the standard Avicel PH-102, of comparable particle size. This can be certainly explained by an uptak e of moisture of the Avicel PH-112 powder as proved experimentally. Th is would limit the use of this material to an air-conditioned room. Th e large particle size product Avicel PH-200 displayed a compactibility close to that of all the other Avicel PH grades (except PH-105), but the highest susceptibility to magnesium stearate. As expected, because it is free-flowing, Avicel PH-200 gave the lowest tablet weight varia bility. Additionnally, the two new grades showed disintegrating proper ties similar to those of Avicel PH-103, PH-102 and PH-101. Finally, on e should bear in mind that the small differences reported here may not be significant because of substantial interbatch variability.