Compaction, compression and drug release characteristics of xanthan gum pellets of different compositions

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 1000-1400 [mu]m) were compacted in a single punch press at maximum punch pressure of 125 MPa using flat-faced punches (diameter of 1.00 cm). 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.http://www.sciencedirect.com/science/article/B6T25-4B8BXPN-B/1/be51e8b55c37493496f79b0f4ae15cc

New sustained release of Zidovudine Matrix tablets − cytotoxicity toward Caco-2 cells

Objective: The aim of this study was to adjust the zidovudine (AZT) release from solid tablets to an ideal profile, by developing matrices comprising swellable polymers with nonswellable ones. Methods: Directly compressed matrices comprised different ratios of hydroxypropylmethylcellulose K15M and K100M, ethylcellulose, and methacrylic acid (Eudragit® RS PO and Eudragit® RL PO) were prepared. Technological characterization and evaluation of the in vitro release behavior were carried out. Cell density and viability following drug exposure were evaluated by the SRB method, for the Caco-2 line, while cell morphology was assessed upon Trypan blue staining. Results: A specific formulation containing 5% of each excipient − HPMC K15M, HPMC K100M, Eudragit® RS PO, and Eudragit® RL PO − was found to yield the best release profile. Application of the Korsmeyer–Peppas model to the dissolution profile evidenced that a non-Fickian (anomalous) transport is involved in the drug release. Regarding the influence of the tablets’ composition on the drug’s cytotoxic effect toward the Caco-2 cell line, a reduction of cell biomass (0–15%) was verified for the distinct AZT formulations tested, F19 having displayed the highest cytotoxicity, after 24 and 48 h of incubation. Additionally, a high reversibility of the AZT effect was observed. Conclusions: The results showed that the simultaneous application of both hydrophilic and hydrophobic polymers can modulate the drug release process, leading to an improved efficacy and patient compliance. All AZT formulations studied were found to be cytotoxic against Caco-2 cells, F19 being the most effective one.J.V.S. acknowledges PhD fellowship from the Programme Alβan, the European Union Programme of High Level Scholarships for Latin America (scholarship no. E06D100103BR)

Compaction, compression and drug release properties of diclofenac sodium and ibuprofen pellets comprising xanthan gum as a sustained release agent

Compaction and compression of xanthan gum pellets were evaluated and drug release from tablets made of pellets was characterised. Two types of pellets were prepared by extrusion-spheronisation. Formulations included xanthan gum, at 16% (w/w), diclofenac sodium or ibuprofen, at 10% (w/w), among other excipients. An amount of 500 mg of pellets fraction 1000-1400 [mu]m were compacted in a single punch press at maximum punch pressure of 125 MPa using flat-faced punches (diameter of 1.00 cm). Physical properties of pellets and tablets were analysed. Laser profilometry analysis and scanning electron microscopy of the upper surface and the surface of fracture of tablets revealed that particles remained as coherent individual units after compression process. Pellets were flatted in the same direction of the applied stress evidencing a lost of the original curvature of the spherical unit. Pellets showed close compressibility degrees (49.9% for pellets comprising diclofenac sodium and 48.5% for pellets comprising ibuprofen). Xanthan gum pellets comprising diclofenac sodium experienced a reduction of 65.5% of their original sphericity while those comprising ibuprofen lost 49.6% of the original porosity. Permanent deformation and densification were the relevant mechanisms of compression. Fragmentation was regarded as non-existent. The release of the model drug from both type of tablets revealed different behaviours. Tablets made of pellets comprising ibuprofen released the model drug in a bimodal fashion and the release behaviour was characterised as Case II transport mechanism (release exponent of 0.93). On the other hand, the release behaviour of diclofenac sodium from tablets made of pellets was anomalous (release exponent of 0.70). For the latter case, drug diffusion and erosion were competing mechanisms of drug release.http://www.sciencedirect.com/science/article/B6T7W-4FR3ND1-1/1/7bebf72d7c381f0ef545c3c20689017