Gastrointestinal Transit of a Solid Indigestible Capsule as Measured by Radiotelemetry and Dual Gamma Scintigraphy

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Abstract
The objectives of the present study were to evaluate gastric and small bowel transit times of an indigestible solid matrix and to characterize the specific changes in intraluminal pH as a function of transit time through the gastrointestinal tract. Particular attention was paid to the lag time at the ileocecal junction. A Heidelberg capsule (HC), labeled with 10 µCi Indium-111, was given orally to six healthy male subjects 15 min after oral ingestion of 100 µCi of 99mTc-sulfur colloid as a liquid fatty meal (4 ml/kg). Intraluminal pH was monitored continuously via the HC. Gastric and small bowel transit of the radionuclides was monitored via external scintigraphy at 0.5-hr intervals. Gastric residence times (GRT) of the HC ranged from 2.8 to 4.8 hr, with a mean (±SD) of 3.6 ± 0.8 hr. These values were independent of the individual's weight, height, or body surface area. Small bowel transit times of the HC ranged from 2.8 to >5.5 hr, which were consistent with the reported values of 3 to 5 hr. The lag times of the HC at ileocecal junction ranged from 0.8 to >2.5 hr. The presence of the lag times at the ileocecal junction in all subjects confirmed that it acts as a valve or sphincter. Mouth-to-cecum transit times of the HC occurred within 9.0 hr in 50% of the subjects. In general, following a sharp rise upon pyloric passage of HC the pH dropped slightly but then increased linearly throughout the small intestine. The mean duodenal pH was 5.8 ± 0.8 and the pH at the ileocecal junction ranged from 6.5 to 8.5, with a mean of 7.3 ± 0.7. Passage through the ileocecal junction was associated with a 0.5- to 1.0-unit rise in pH in three subjects who exhibited passage of the HC into the large bowel within the study period. The present data may have implications in the designing of more effective dosage forms with specific delivery to proximal or distal small bowel regions.