Synthetic dilators compared to Laminaria reached higher maximum diameters, acted faster, were more consistent and were able to expand against force three times more. The results support clinical observations that synthetic dilators are more suitable and preferable for same-day D&E procedure and that fewer synthetic dilators are needed to achieve the same effect.

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The new type of hydrogel system (which is known under the trademark HYPAN™), is described in some detail here, emphasizing its grades and those properties potentially useful in controlled drug delivery systems. HYPAN hydrogels are distinguished by a physical network of crystalline clusters which fully replace the covalent network typical of other hydrogels. As a result, HYPAN hydrogels can be processed by a number of methods unusual for hydrogels, such as extrusion, injection molding and the like. The crystalline network also provides HYPAN with improved mechanical properties at higher water contents, which in turn allows for higher permeabilities of aqueous solutes. The combination of improved mechanical properties and permeabilities with improved processability and good biocompatibility is believed to open some new possibilities in targeted and controlled drug delivery. This paper is written as an overview of the compositions, structures and essential properties of HYPAN materials. It will soon be followed by more detailed studies in selected areas.

Measurements of the permeability coefficients of various compounds up-to a molecular weight of about 70,000 have shown clearly that membranes prepared from hydrolyzed polyacrylonitrile are about 10 times more permeable than those made of poly(2-hydroxyethyl) methacrylate. The higher permeability is probably due more to the higher water content (about 75%) than to the type of network. The high mechanical strength of the membranes and their good permeability to compounds possessing a comparatively high molecular weight seem to designate the material for some new applications in medicine.

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