The effect of muscarinic blockade on anorectal function in patients with constipation-predominant irritable bowel syndrome

Abstract

Anorectal manometry was performed after giving 5 mg of cimetropium bromide, an antimuscarinic compound, and placebo intravenously, according to a crossover design, to 13 patients with constipation, chronic abdominal pain, and normal or slightly delayed intestinal transit in the left colon. Patients with delayed transit in each of the colonic segments and with anal or pelvic floor pathology were excluded. Anal resting tone and internal anal sphincter relaxation were in the upper area of the normal range; rectal sensitivity in the lower. Motor and sensitivity parameters did not show any significant difference after cimetropium and placebo, apart from the threshold to onset of painful sensation, which was reduced after cimetropium. Previous studies have shown that anticholinergic agents inhibit the increased sigmoid colon motility in patients with irritable bowel syndrome. Our study shows that in painful constipation (a clinical variety of irritable bowel syndrome), the anorectal motor parameters are not modified by the muscarinic blockade as it occurs in the sigmoid colon. Moreover, these results confirm that internal anal sphincter resting tone and its relaxation due to rectal distention are not cholinergically modulated.