Background and Aims: This study evaluated the effects of a partial 5- hydroxytryptamine (5-HT)4 agonist, tegaserod, on gastric small bowel and colonic transit in constipation-predominant irritable bowel syndrome (IBS). Methods: After a 1 week run-in period, 24 patients with constipation- predominant IBS were randomized to 1 week of tegaserod, 2 mg twice daily, or placebo treatment. Scintigraphic gastric emptying, small bowel transit, and colonic transit were determined before administration of study drug and after 1 week on the medication. Colonic transit was also measured using radiopaque markers and a single radiograph on day 5. Results: Gastric emptying was unaltered by tegaserod. Proximal colonic filling at 6 hours, a measure of orocecal transit, was accelerated by tegaserod (70.4% ± 1.3% [mean ± SEM] vs. placebo, 46.4 ± 1.9; P = 0.015). Proximal colonic emptying half-time and geometric center at 48 hours were also accelerated by tegaserod compared with baseline, but not compared with placebo. Mean colonic transit time was similar in both groups at baseline and after drug administration (tegaserod, 59.5 ± 2.1 hours; placebo, 62.1 ± 2.1 hours). Conclusions: Tegaserod accelerates orocecal transit, tends to accelerate coIonic transit, and deserves further study in patients with constipation-predominant IBS.
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