| In the present study, gastric emptying of nondigestible solid particles, as well as fine powders, was studied in the fasted dog implanted with a permanent duodenal cannula, located approximately 15 cm from the gastroduodenal junction. Particles of varying sizes (0.5-6.4 mm), density (0.5-3.0 gm/cm{dollar}sp3{dollar}) and surface characteristics were coadministered orally with varying volumes of saline. Avicel powders (sg. gr. 1.5), contained in a '00' capsule or compressed into rapidly disintegrating tablets, were coadministered with varying volumes of saline. To assess the effect of dispersion on the gastric emptying of these powders, the same amount of powders used in the above studies was dispersed in an appropriate volume of saline, and the resulting suspension was administered to fasted dogs. Effluent particles and powders were collected from the duodenal cannula. The phase of the motility pattern was ascertained by the appearance of bile, which occurs during phase II, as well as mucus discharge, which occurs in phase III and stops at the onset of phase I.; In the fasted dog, gastric emptying of nondigestible particles and powders closely followed the gastric motility pattern. Onset of discharge of particles and powders correlated with late phase II and phase III activity. Except for a few cases, which took two migrating motor complexes (MMC), more than 90% of administered particles and 80% of the powders was discharged form the stomach after one MMC. The discharged particles and powders were entrapped within mucous plugs.; Gastric emptying of nondigestible particles was independent of size, density and surface characteristics as well as volume of coadministered saline; and gastric emptying of powders was unaffected by disintegration time, extent of dispersion in the stomach, and volume of coadministered saline. Mucus seemed to play a significant role in the distribution and discharge of administered particles and powders. It appears that the residence time of oral dosage forms in the fasted, canine stomach is primarily dictated by two factors: the phasic activity of the motility pattern at the time of ingestion and the bolus discharge due to particle-mucus interactions. |
