Effects of propranolol on colonic pressure in patients with irritable bowel syndrome

The effect of propranolol on colonic motility was studied in 10 patients with irritable bowel syndrome. Colonic motility was recorded by pressure measurement 15-18 cm from the anus, and total contractile activity (kPa x min) simultaneously integrated. After rest, motility was recorded for 30 min after injection of saline (control period) and after injection of 5 mg propranolol intravenously. Administration of propranolol was followed by an increase in colonic motility in 9 out of the 10 patients. In one patient no change was observed. During the control period, total contractile activity was 7.7 +/- 18 (S.E.M.) kPa x min (58 +/- 14 mmHg x min), increasing after propranolol to 14.2 +/- 2.3 kPa x min (107 +/- 17 mmHg x min). The difference was significant (p less than 0.01). After propranolol, the colonic pressure waves regularly appeared for longer periods of time and had higher amplitudes than during control activity. Prolonged elevation of basal pressure with superimposed pressure waves was observed in two patients. This study shows that adrenergic beta-blocking agents enhance colonic motility in man. The results may explain abdominal symptoms such as pain and change in bowel habits appearing in patients treated with beta-blocking drugs.