Evaluation of peroral silicone dosage forms in humans by gamma-scintigraphy

Gastric emptying of oral silicone dosage forms was studied in humans by gam ma-scintigraphy. To achieve a constant and predictable residence time in th e stomach, three different formulations based on known concepts such as con trolled swelling were investigated. The importance of physical parameters s uch as size or shape were also examined to assess the feasibility of design ing a dosage form for gastric retention. Three shapes: minimatrices, extrud ed rods and moulded slabs were screened. To label the silicone polymer, two isotopes, used routinely in nuclear medicine departments, were selected: i odine-123 and indium-111. To select the most suitable isotope, the yield an d the stability of the labelling were determined in vitro on the pharmaceut ical dosage forms. The residence time of these silicone formulations, label led with iodine and administered in hard gelatine capsules, was monitored i n 12 subjects with a gamma camera. The study was performed under fed condit ions after ingestion of a standardised meal labelled with indium. The minim atrices provided at least 3 h retention, slabs exhibited 4 h 40 min retenti on. For the rods the mean residence time in the stomach was around 4 h 20 m in. In addition, a correlation was established between the gastric emptying of rods and the half-gastric residence time of meal. On the contrary, such a correlation was not observed for the slabs. (C) 1999 Elsevier Science B. V. All rights reserved.