Comparison of selective M3 and nonselective muscarinic receptor antagonists on gastrointestinal transit and bowel habits in humans

Adil E. Bharucha, Karthik Ravi, Alan R. Zinsmeister

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Although in vitro studies show that muscarinic M3 receptors primarily mediate the effects of acetylcholine on gastrointestinal contractility, the muscarinic receptor subtypes regulating gastrointestinal motor activity and transit in humans in vivo are unclear. We hypothesized that muscarinic M3-specific but not nonspecific receptor antagonists would delay gastrointestinal and colonic transit in humans. In this parallel-group study, gastric emptying, small intestinal transit, and colonic transit were assessed by scintigraphy on days 4-6 in 72 healthy subjects (49 women) who received placebo (n = 16), the M3 antagonist darifenacin ER [7.5 mg (n = 20) or 15 mg daily (n = 17)], or the nonspecific antagonist tolterodine [4 mg daily (n = 19)] for 6 days. Bowel habits were recorded by daily diaries. Both doses of darifenacin substantially delayed [P < 0.01 vs. placebo (for both doses), P < 0.01 vs. tolterodine (for 15 mg)] small intestinal transit, i.e., colonic filling at 6 h (placebo [59.6 ± 6.4%, mean ± SE], 7.5 mg ER [34.4 ± 6.1%], 15 mg ER [20.4 ± 6.3%)]. Darifenacin (15 mg) also delayed (P < 0.01 vs. placebo and tolterodine) half-time for ascending colonic emptying [placebo (12.0 ± 1.5 h), 7.5 mg (18.6 ± 1.9 h), 15 mg (22.9 ± 2.6 h)] and colonic transit (geometric center) at 24 [placebo (2.8 ± 0.2), 7.5 mg (2.4 ± 0.2), 15 mg (1.9 ± 0.2)] but not 48 h. Darifenacin did not affect gastric emptying and tolterodine did not affect bowel habits or gastrointestinal transit. With muscarinic antagonists used at clinically approved doses, these findings demonstrate that muscarinic M3 receptors regulate small intestinal and colonic transit in humans; colonic effects are more pronounced in the right than left colon. At doses that affect small and large intestinal transit, M3 antagonists do not affect gastric emptying in humans. The efficacy of darifenacin in diarrhea-predominant irritable bowel syndrome should be evaluated.

Original languageEnglish (US)
Pages (from-to)G215-G219
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Issue number1
StatePublished - Jul 2010


  • Cholinergic
  • Colonic
  • Irritable bowel syndrome
  • Motility
  • Small intestine

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)


Dive into the research topics of 'Comparison of selective M3 and nonselective muscarinic receptor antagonists on gastrointestinal transit and bowel habits in humans'. Together they form a unique fingerprint.

Cite this