Development and Characterisation of Gastroretentive Solid Dosage Form Based on Melt Foaming

Dosage forms with increased gastric residence time are promising tools to increase bioavailability of drugs with narrow absorption window. Low-density floating formulations could avoid gastric emptying; therefore, sustained drug release can be achieved. Our aim was to develop a new technology to produce low-density floating formulations by melt foaming. Excipients were selected carefully, with the criteria of low gastric irritation, melting range below 70°C and well-known use in oral drug formulations. PEG 4000, Labrasol and stearic acid type 50 were used to create metronidazole dispersion which was foamed by air on atmospheric pressure using in-house developed apparatus at 53°C. Stearic acid was necessary to improve the foamability of the molten dispersion. Additionally, it reduced matrix erosion, thus prolonging drug dissolution and preserving hardness of the moulded foam. Labrasol as a liquid solubiliser can be used to increase drug release rate and drug solubility. Based on the SEM images, metronidazole in the molten foam remained in crystalline form. MicroCT scans with the electron microscopic images revealed that the foam has a closed-cell structure, where spherical voids have smooth inner wall, they are randomly dispersed, while adjacent voids often interconnected with each other. Drug release from all compositions followed Korsmeyer-Peppas kinetic model. Erosion of the matrix was the main mechanism of the release of metronidazole. Texture analysis confirmed that stearic acid plays a key role in preserving the integrity of the matrix during dissolution in acidic buffer. The technology creates low density and solid matrix system with micronsized air-filled voids

Revisiting the relation between environmental performance and environmental disclosure: An empirical analysis

Previous empirical evidence provides mixed results on the relationship between corporate environmental performance and the level of environmental disclosures. We revisit this relation by testing competing predictions from economics based and socio-political theories of voluntary disclosure using a more rigorous research design. In particular, we improve on the prior literature by focusing on purely discretionary environmental disclosures and by developing a content analysis index based on the Global Reporting Initiative sustainability reporting guidelines to assess the extent of discretionary disclosures in environmental and social responsibility reports. This index better captures firm disclosures related to its commitment to protect the environment than the indices employed by prior studies. Using a sample of 191 firms from the five most polluting industries in the US, we find a positive association between environmental performance and the level of discretionary environmental disclosures. The result is consistent with the predictions of the economics disclosure theory but inconsistent with the negative association predicted by socio-political theories. Nevertheless, we show that socio-political theories explain patterns in the data (“legitimization”) that cannot be explained by economics disclosure theories. 2007 Elsevier Ltd. All rights reserved