Bioavailability study of Theo-dur tablets in the fasted cannulated dog

The present study uses the cannulated dog to verify the major elements of gastrointestinal (GI) motility affecting the performance of oral sustained release dosage forms. It appears that the residence time of a Theo-dur tablet in the fasted canine stomach and small intestine is dictated by the phasic activity of the motility pattern at the time of ingestion. The tablet does not disintegrate in vivo but undergoes surface erosion. Onset of tablet discharge corresponded with late phase II and phase III activity. The discharged eroded tablet was entrapped within mucus plugs. Mucus may play a significant role in the dissolution of administered tablets. There is little variability in the duodenal and ileal effluent pH, observed after onset of Theo-dur tablet discharge.