Effect of Bisacodyl on Intestinal Electrolyte and Water Net Transport and Transit

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Abstract
The effect of bisacodyl on intestinal electrolyte, glucose, and water transport, and transit was studied in 6 healthy volunteers by intestinal perfusion. A 5-lumen tube with an occluding balloon allowed constant perfusion (10 ml/min) of 30 cm of the upper jejunum and a rapid collection of the perfusate free of contaminants. A phenol red bolus was injected into the tube and its passage through the test segment was calculated by dye dilution formula. A 1-hour control period was followed by a test period with 6 mg/h bisacodyl and followed by 2 other 1-hour control periods. Net absorption of Na+ (0.35 ± 0.08 mmol/min) and water (1.7 ± 0.6 ml/min) changed to net secretion (Na+ -0.93 ± 0.3 ml/min; water -6.6 ± 1.9 ml/min), glucose absorption decreased from 25.4 ± 1.1 to 6.3 ± 0.5 mg/min and K secretion was enhanced. 62 ± 2.1% of bisacodyl was absorbed in the 30-cm jejunal segment. Mean transit time decreased from 8.5 ± 1 to 4.4 ± 0.7 min and mean flow rate increased from 8.4 ± 0.6 to 16.6 ± 1.9 ml/min. There was an inverse linear relationship between mean transit time and mean flow rate. All the effects of bisacodyl were fully or at least partially reversible. Volume and calculated radius of the test segment remained constant and did not change under bisacodyl. It is concluded, that the secretory effect of bisacodyl is mainly responsible for the decreased mean transit time rather than a direct effect on motility.