Influence of chitosan concentration on mechanical and release properties of metronidazole tablet

Abstract

Background: Chitosan is a widely used pharmaceutical polymer and it serves different purposes in tablet formulations.

Objective of study: This work was aimed at assessing the impact of chitosan concentration on the mechanical and release properties of metronidazole tablet.

Methodology: Seven batches of metronidazole tablets (500 mg weight) containing 40 % drug and 33 % microcrystalline cellulose were made to contain crab shell chitosan at concentrations of 0, 2.5, 5.0, 7.5, 10, 15 and 20 %w/w for batches 1–7 respectively and then produced by direct compression. The tablets were assessed for crushing strength, friability, compact density, disintegration time and dissolution rate. Porosity, crushing strength–friability index (CS-FR) and crushing strength-friability-disintegration time index [(CS-FR)/DT] were calculated. Data were analyzed using GraphPad Instat-3 software.

Results: Crushing strength decreased while friability and porosity increased with increase in concentration of chitosan. The disintegration times were 4.54, 2.49, 12.66, 16.85, 18.29, 22.26 and 32.97 min for F1, F2, F3, F4, F5, F6 and F7 respectively. There were significant differences in both CS-FR and (CS-FR)/DT indices. The (CS-FR)/DT indices were 5.04, 6.18, 1.00, 0.71, 0.56, 0.40 and 0.22 for F1 to F7 respectively. Dissolution rate decreased with increase in chitosan concentration.

Conclusion: Low concentrations of chitosan (5.0 %w/w and below) in tablets are characterized by good mechanical and immediate release properties. The use of chitosan at higher concentration for any purpose should be in conjunction with an excipient that will impart good mechanical strength.

Keywords: Crab shell chitosan, mechanical properties, release properties