THE TRANSIT RATE OF DIFFERENT-SIZED MODEL DOSAGE FORMS THROUGH THE HUMAN COLON AND THE EFFECTS OF A LACTULOSE-INDUCED CATHARSIS

Gamma scintigraphy has been used to compare the colonic transit rate of different sizes of radiolabelled model dosage forms in healthy human subjects. Studies simultaneously compared the ascending colon residence time of In-111-labelled 0.2 mm ion-exchange resin particles and Tc-99m-labelled 5 or 8.4 mm non-disintegrating tablets. Under normal conditions, no difference was observed between the rate of transit through the ascending colon of 0.2 mm particles vs 5 mm tablets (n = 11) or 0.2 mm particles vs 8.4 mm tablets (n = 10). The mean period of residence of 50% of the administered 0.2 mm particles in the ascending colon was 11.0 +/- 4.0 h (n = 21). Coadministration of the laxative, lactulose, to subjects receiving the 0.2 and 5 mm particles significantly accelerated colonic transit. Under these conditions, the ascending colon residence of the 0.2 mm resin was significantly shorter than for the 5 mm tablets, although the magnitude of the effect was small.