Part III: Hormonal Influences

Functional diarrhoea

Functional diarrhoea remains an elusive and a difficult condition to diagnose and treat; however, with careful history-taking a logical approach to management can be made. Each patient must be considered individually and sub-classification should be attempted. It is very important to rule out organic disease. Unfortunately treatment remains empirical in the majority of cases, but more is now known about functional disorders and there is hope for the future.

Effects of beta-adrenoceptor blocking drugs on human sigmoid colonic motility

Effects of propranolol and metoprolol on sigmoid colonic motility were studied in 12 healthy volunteers in a double-blind randomized fashion. Colonic pressure was recorded 15-18 cm from anus and contractile activity quantified for periods of 25 min. On separate days propranolol, metoprolol, and placebo, respectively, was administered intravenously preceded by a control period. After propranolol, 10 mg intravenously, pressure activity increased significantly from 3.8 +/- 1.1 (SEM) kPa X min (28 +/- 8 mm Hg X min) to 5.9 +/- 1.0 kPa X min (44 +/- 8 mm Hg X min) (P less than 0.001). Also, after propranolol, 5 mg intravenously, the pressure activity was increased (P less than 0.05). After metoprolol, 10 mg intravenously, contractile activity increased from 4.3 +/- 0.9 kPa X min (32 +/- 7 mm Hg X min) to 6.1 +/- 1.0 kPa X min (46 +/- 8 mm Hg X min) (P less than 0.01). The two drugs caused equipotent reduction of heart rate. After placebo, no effect on sigmoid pressure or heart rate was observed. The study shows that unselective (propranolol) and beta 1-selective (metoprolol) beta-blocking drugs enhance distal colonic pressure in man. Colonic motility seems to be under sympathetic beta-adrenergic influence even under fairly unstrained conditions.

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.