Influence of Senna, Fibre, and Fibre + Senna on Colonic Transit in Loperamide-Induced Constipation

Retarded colonic transit and disturbed defecation are the most prominent pathophysiological mechanisms in constipation. Both may be influenced by bulking agents and by laxatives such as senna. Direct measurements of the influence of such substances on colonic transit are rare mainly because of technical problems. We measured gastric emptying, small and large intestinal transit in 24 healthy volunteers by a newly developed method employing a metal detector. Twelve persons taking a normal diet received loperamide in a dose sufficient to double the individual transit time. All subjects measured gastrointestinal transit time under normal conditions and with Sennatin containing purified sennosides 20 mg, Agiocur (30 g) as a fibre product containing 20 g Plantago ovata seeds/husks, or Agiolax (10 g) as a combination of 5.4 g P. ovata seeds/husks + 1.2 g senna pod with a sennoside content of 30 mg. Colonic transit was reduced by Sennatin and by Agiolax from 39 ± 4 h to 17 ± 3 h (p < 0.005). Agiocur did not influence colonic transit (39 ± 3 h). Loperamide prolonged colonic transit from 27 ± 0.7 to 72 ± 12 h. This effect was abolished by Sennatin (30 ± 5 h) and Agiolax (27 ± 1 h) (p < 0.005), but not by Agiocur (64 ± 13 h). The same effects were seen when right and left colonic transit were analyzed separately. Neither gastric emptying nor small intestinal transit were affected by either substance. All of the three study drugs increased stool weight significantly (p < 0.05). When stool frequency and consistency were compared, the effects were less clear. Agiolax caused the greatest, Agiocur the least changes of these parameters. Oroanal transit times measured by the metal detector and by the Hinton method using 20 radioopaque markers were similar (43 ± 6 and 47 ± 6 h, respectively). Sennosides alone as well as in combination with P. ovata seeds, but not fibre alone, shortened colonic transit time to half of the original value and abolished the effect of loperamide-induced constipation. The effect of bulking agents on colonic transit time is inferior to the efficacy of senna. The combination of both agents is not superior to sennosides alone at least under normal dietary conditions.