Polymer film formulations for the preparation of enteric pharmaceutical capsules

Objectives Standard pharmaceutical capsules are designed to dissolve in the acidic environment of the stomach releasing the encapsulated contents for absorption. When release is required further along the gastrointestinal tract capsules can be coated with acid insoluble polymers to enable passage through the stomach and dissolution in the intestine. This paper describes formulations that have the potential to be used to produce two-piece hard capsules for post-gastric delivery without the requirement of an exterior coat. Methods The formulation uses three polysaccharides: sodium alginate, hypromellose and gellan gum to provide acid insolubility and the ability to form a capsule using standard industrial equipment. Key findings The rheological profile on cooling, of the base material, water content and thickness of the films were shown to be comparable with those of commercial capsules. The capsules remained intact for 2 h in 100 mM HCl at pH 1.2 and within 5 min of being removed from the acid and submerged in phosphate-buffered saline at pH 6.8 were ruptured. Conclusions Selected formulations from this study have potential for use as delayed release capsules

Wave-ice interactions in the marginal ice zone. Part 1: Theoretical foundations

A wave-ice interaction model for the marginal ice zone (MIZ) is reported that calculates the attenuation of ocean surface waves by sea ice and the concomitant breaking of the ice into smaller floes by the waves. Physical issues are highlighted that must be considered when ice breakage and wave attenuation are embedded in a numerical wave model or an ice/ocean model.The theoretical foundations of the model are introduced in this paper, forming the first of a two-part series. The wave spectrum is transported through the ice-covered ocean according to the wave energy balance equation, which includes a term to parameterize the wave dissipation that arises from the presence of the ice cover. The rate of attenuation is calculated using a thin-elastic-plate scattering model and a probabilistic approach is used to derive a breaking criterion in terms of the significant strain. This determines if the local wave field is sufficient to break the ice cover. An estimate of the maximum allowable floe size when ice breakage occurs is used as a parameter in a floe size distribution model, and the MIZ is defined in the model as the area of broken ice cover. Key uncertainties in the model are discussed. © 2013 Elsevier Ltd.Timothy D. Williams, Luke G. Bennetts, Vernon A. Squire, Dany Dumont, Laurent Bertin