Scintigraphic verification of adherence of a chitosan formulation to the human oesophagus.

It is well known that adherence of a drug product, e.g. a gelatine capsule, to the oesophagus can cause oesophageal injury, which can be severe if the medicinal agent has corrosive properties. In a recent study we investigated by means of gamma scintigraphy whether chitosan granules dispensed in gelatine capsules had gastro-retentive properties. In one of ten volunteers the formulation lodged in the oesophagus. This case is reported here. The capsule adhered initially to the distal oesophagus. The capsule shell had started to disintegrate within 5 min, with some radioactivity detectable in the stomach. However, about two thirds of the radioactivity remained detectable in the oesophageal region for 1.75 h. This could be explained on the basis that there had been adherence not only of the gelatine shell but also of chitosan granules to the oesophageal mucosa. In evaluating potential for causing oesophageal injury it is not enough to consider only the mucoadhesive properties of the outermost layer of a drug product, because the filler may also have such properties. When new excipient materials are introduced, evaluation of their mucoadhesive tendencies is important.