Effect of a calcium channel blocker and antispasmodic in diarrhoea-predominant irritable bowel syndrome

Background: Irritable bowel syndrome (IBS) is a colonic function disorder. Both pinaverlum bromide (a selective calcium channel blocker) and mebeverine (an antispasmodic) are reported to be effective in the long-term (12-16 weeks) treatment of IBS patients. Their efficacy in the short-term treatment of IBS patients and colonic transit time is unclear. Furthermore, substance P and neuropeptide Y have either excitatory or inhibitory effects on colonic motility. Whether the efficacy of both drugs is mediated through these neuropeptides remains unknown. Methods and Results: A clinical trial was conducted with 91 patients with diarrhoea-predominant IBS. After basal measurement of the total colonic transit time, IBS patients were randomized to receive either pinaverlum bromide (50 mg, t.i.d.) or mebeverine (100 mg, t.i.d.) for 2 weeks. The symptomatic scores regarding defaecation, total colonic transit time and serum levels of substance P and neuropeptide Y were measured before and after treatments. The daily defaecation frequency was markedly decreased after treatment (pinaverlum bromide, 2.9 +/- 1.2 vs 2.0 +/- 1.0, P < 0.05; mebeverine, 2.7 +/- 1.1 vs 2.1 +/- 1.0, P < 0.05). The stool consistency became well formed after both treatments (P < 0.05). Both drugs similarly improved the global well-being in these IBS patients (pinaverlum bromide vs mebeverine 73.4: vs 71,8%, P > 0.05). The total colonic transit time was significantly prolonged only after pinaverlum bromide treatment (21.4 +/- 15.5 vs 30.8 +/- 14.8 h, P < 0.01). Neither substance P nor neuropeptide Y serum level was significantly changed after either treatments. Conclusion: Pinaverlum bromide and mebeverine have similar therapeutic efficacies on diarrhoea-predominant IBS patients. Prolonged colonic transit time may be one of the factors responsible for the efficacy of pinaverlum bromide on the IBS patients. Substance P and neuropeptide Y appear less important in the pathogenesis of diarrhoea-predominant IBS. (C) 2000 Blackwell Science Asia Pry Ltd.