Colonic transit scintigraphy labeled activated charcoal compared with ion exchange pellets.

UNLABELLED: Scintigraphic measurement of colonic transit is currently performed by delivering 111In ion exchange resin pellets to the colon in a methacrylate-coated capsule. However, use of this method is constrained by the need for an investigational drug permit. We have demonstrated previously optimal adsorption in vitro of commonly used radioisotopes (e.g., 99mTc or 111In) to activated charcoal in milieus that mimicked gastric and small intestinal content. The aim of this study was to compare the transit profiles of radioactive activated charcoal and resin pellets delivered to the colon in the same methacrylate-coated capsule.
METHODS: In 10 healthy volunteers, we compared the colonic transit profiles over 32 hr of simultaneously administered resin pellets labeled with 111In and activated charcoal mixed with 99mTc-diethylenetriaminepentaacetic acid. Transit was summarized as the geometric center (weighted average of counts) in the colon at each scanning period.
RESULTS: Colonic transit profiles were virtually identical with the two markers, with less than 0.1 geometric center unit differences in the transit profiles over the 32-hr periods.
CONCLUSION: Activated charcoal is a suitable alternative to resin pellets when delivered in a methacrylate-coated, delayed-release capsule to the colon for measurement of transit by scintigraphy.