Viscometric study of polyacrylic acid systems as mucoadhesive sustained-release gels.

This report describes a novel nonaqueous polymeric formulation that exhibits low-viscosity fluid behavior for ease of spraying with conventional nebulizer, which when sprayed into the nasal cavity, transforms to a high-viscosity gel for efficient retention and drug absorption. The transformation occurs because of the rheological changes induced by a change in the solvent composition of the polymeric formulation in the moist nasal cavity. Such a rheological change would then facilitate enhanced residence time of the drug at the site of administration in order to avoid drainage losses. This study reports the results of the effects of a variety of factors such as solvent composition and polymer concentration on the rheological properties of a polyacrylic acid polymer. An attempt to correlate viscosity enhancement effects with enhanced and sustained-release behavior of propranolol, a drug that undergoes extensive first-pass effects, from such formulations via nasal administration in beagle dogs is also described.