Effect of lactose, lactulose and bisacodyl on gastrointestinal transit studied by metal detector

To study the effect of 45 g lactose, 30 g lactulose and 10 mg bisacodyl on gastrointestinal transit in 30 healthy volunteers by metal detector and Hinton marker method. The first set of measurements were performed under standard conditions. In a second stage, transit was slowed to twice the original value by loperamide to simulate constipation conditions.

Bisacodyl drastically accelerated small and large intestinal transit. Colonic transit was shortened to 23% and to 31% of control values, without and with loperamide. Bisacodyl increased stool weight and decreased stool consistency in all persons. Lactulose marginally shortened small intestinal transit (P = 0.08) but significantly increased stool weight and decreased stool consistency. The accelerating effect of lactose on small intestinal transit was abolished by loperamide. Lactose did not influence colonic transit, stool weight or stool consistency. Results of metal detector and Hinton marker method corresponded well (r = 0.75), the metal detector method measuring slightly shorter transit times than the Hinton marker method.

With the dose chosen in this trial, lactose did not have any laxative effect in lactose tolerant persons. Laxative effect was mild with lactulose and most pronounced with bisacodyl.