title: Compaction, compression and drug release characteristics of xanthan gum pellets of different compositions.
abstract: Compaction and compression of xanthan gum (XG) pellets were evaluated and drug release from tablets made of pellets was characterised. Three formulations were prepared by extrusion-spheronisation and included, among other excipients, diclofenac sodium (Dic Na), at 10% (w/w); xanthan gum, at 16% (w/w); and one of three different fillers (lactose monohydrated (LAC), tribasic calcium phosphate (TCP) and beta-cyclodextrin (beta-CD)), at 16% (w/w). Five hundred milligrams of pellets (fraction 1000-1400microm) were compacted in a single punch press at maximum punch pressure of 125MPa using flat-faced punches (diameter of 1.00cm). Physical properties of pellets and tablets were analysed. Dissolution was performed according to the USP paddle method. Pellets showed close compressibility degrees (49.27% LAC; 51.32% TCP; and 50.48% beta-CD) but densified differently (3.57% LAC; 14.84% TCP; 3.26% beta-CD). Permanent deformation and densification were the relevant mechanisms of compression. Fragmentation was regarded as non-existent. The release behaviour of tablets made of pellets comprising LAC or beta-CD was anomalous having diffusional exponent (n) values of 0.706 and 0.625, respectively. Drug diffusion and erosion were competing mechanisms of drug release from those tablets.
authors.affiliation: Faculdade de Farmácia, Centro de Estudos Farmacêuticos, Universidade de Coimbra, Rua do Norte, 3000-295, Coimbra, Portugal. helton@ci.uc.pt
authors.forename: Helton
authors.initials: H
authors.lastname: Santos
authors.forename: Francisco
authors.initials: F
authors.lastname: Veiga
authors.forename: Ma Eugénia
authors.initials: ME
authors.lastname: Pina
authors.forename: João José
authors.initials: JJ
authors.lastname: Sousa
mesh_terms: D002130:Calcium Phosphates / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D019245:Compressive Strength; D004008:Diclofenac / Q000737:chemistry; D004339:Drug Compounding; D005079:Excipients / Q000737:chemistry*; D010316:Particle Size; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D016062:Porosity; D011208:Powders; D013499:Surface Properties; D013607:Tablets / Q000737:chemistry*; D013997:Time Factors; D047392:beta-Cyclodextrins / Q000737:chemistry
chemical_list: D002130:Calcium Phosphates; D005079:Excipients; D011135:Polysaccharides, Bacterial; D011208:Powders; D013607:Tablets; D047392:beta-Cyclodextrins; D004008:Diclofenac; C031215:betadex; C018392:tricalcium phosphate; C002563:xanthan gum