Oesophageal bioadhesion of sodium alginate suspensions 2. Suspension behaviour on oesophageal mucosa.

Sodium alginate suspensions in a range of water miscible vehicles were investigated as novel bioadhesive liquids for targeting the oesophageal mucosa. Such a dosage form might be utilised to coat the oesophageal surface and provide a protective barrier against gastric reflux, or to deliver therapeutic agents site-specifically. Alginate suspensions swelled and formed an adherent viscous layer on contact with the mucosa. The swelling kinetics of alginate particles on the oesophageal surface was examined with respect to vehicle composition and related to the extent, duration and location of bioadhesion within the oesophagus. Mucosal retention was evaluated in two in vitro models utilising tissue immersion and a peristaltic tube. By varying the vehicle composition it was possible to modulate the rate of swelling of alginate particles on the mucosa and the mucosal retention of suspensions. Suspensions containing predominantly glycerol exhibited superior retention and were preferentially retained within the lower oesophagus. The propensity of these suspensions to rapidly swell on the mucosa and establish adhesive/cohesive bonds may explain their enhanced retention. The potential to control, through vehicle composition, the extent, duration and location of oesophageal retention could provide a useful tool for site targeting of viscous polymers to the oesophagus.