Mebeverine decreases mass movements and stool frequency in lactulose-induced diarrhoea

Background: In spite of its frequent use in the treatment of irritable bowel disease little is known about mebeverine’s mode of action in man. Aim: To examine mebeverine’s effect on transit though the gut during lactulose-induced diarrhoea. Methods: Nine healthy volunteers undertook a two-way randomized crossover study. Diarrhoea was induced using lactulose pre-treatment (20 m t.d.s., 4 days) and subjects received either mebeverine (135 mg t.d.s.) or no treatment. Transit of two enteric-coated capsules containing radiolabelled 8.4 mm tablets and 180–250 μM ion exchange resin were followed using gamma scintigraphy. Stool frequency and symptoms were assessed by diary cards. Results: Mebeverine reduced mean daily stool frequency associated with lactulose ingestion from a median of 2.25 (interquartile range (IQR) 1.75–2.75) to 1.5 (IQR 1.25–2.25) movements. Mebeverine significantly reduced the number of mass movements observed in the colon during the 11 h of the study from 2 (2–2) to 1 (1–2), and the number of retrograde movements from 1 (0–2) to 0 (0–0) (P < 0.05). Mebeverine did not significantly alter the gastric emptying rate of the intact capsule (2.9 (1.9–3.2) to 2.8 (2.6–4.0) h) however it induced a small but significant acceleration in small intestinal transit of the capsule (1.6 (0.8–2.0) h to 1.0 (0.52–1.32) h, P = 0.02). Conclusion: Mebeverine reduces the diarrhoeal effect of lactulose by decreasing the mass movements induced in the ascending colon. This effect may contribute to its clinical effect in irritable bowel syndrome.