The present invention relates to solid dosage forms comprising coatings based on natural ingredients, such as naturally-occuring esterified and non-esterified polyuronic acids, optionally in combination with stabilising lipophilic component(s) (e.g. surfactant(s)) and/or other stabilising components. The inventors have made the surprising discovery that polysaccharide-based coatings can be stabilised, and often imparted with gastric resistant properties, through the inclusion of particular additives and/or additional layers. In particular, polyuronic acid-containing coatings may be stabilised and rendered more robust through the inclusion of a lipophilic component (e.g. surfactant), an esterified polyuronic acid, and/or the deployment of an additional coating layer containing stabilising agents that affect the disintegration and/or dissolution of the polyuronic acid. The polyuronic acid-containing coatings of the invention can exhibit retarded disintegration at gastric pH whilst remaining readily disintegratable at higher pHs. As such, the coatings of the invention provide inter alia promising candidates for enteric coatings.