Effect of particle size of granules on some mechanical properties of paracetamol tablets

Solid dosage forms are invariably multiparticulate systems of heterogenous particle size distribution. The purpose of this study was to investigate the effect of particle size distribution of paracetamol granules on some tablet mechanical properties of paracetamol tablets. Granules were formed by wet massing paracetamol powder (200 g) with 20% (w/w) of maize starch mucilage as binder. Resulting granules were classified into different size fractions (212 1700 μm) by sieve analysis and samples of granules from the various size fractions were compressed into tablets of weight 500 ± 4.3 mg, diameter 12.3 ± 2.3 mm and thickness 3.6 ± 1.2 mm, using a single punch tablet machine at a compression pressure load of 7 arbitrary units on the load scale. The tablets were equilibrated for 24 h before evaluation. Tablet mechanical parameters evaluated were packing fraction (Pf), tensile strength (T), particle density, porosity and friability. The results showed that T values and friability index decreased slightly from 1.48 MNm to 1.35 MNm and 1.77 to 0.93%, respectively, following an increase in the granule sizes from 212 to 1700 μm. These differences were, however, not statistically significant. The packing fraction (Pf) of the tablets increased from 0.853 to 0.960 significantly following an increase in granule size from 212 to 1700 μm. The indication is that there is a higher degree of consolidation of the compacts formed from larger granules as a result of plastic deformation and fragmentation than those from smaller granules. The study showed that varying the granule size distribution in a powdered bed affects some tablet mechanical characteristics. The implication of this is that the granule sizes should be controlled during tableting and/or filling into capsule in order to avoid weight and content variation while ensuring that only tablets with desirable mechanical characteristics are formed.