Comparison of two bowel preparations for colonoscopy : Senna versus sodium phosphate solution

Abstract

Objectives: To determine the efficacy of senna for bowel preparation before colonoscopy. Design: Randomized controlled equivalence trial. Setting: Department of Surgery, Faculty of Medicine, Ramathibodi Hospital. Method: A baseline clinical assessment and laboratory test is done on one hundred and thirty-four patients who need colonoscopy. They are randomly allocated to take 300 mg senna or 95ml. sodium phosphate solution on the day before colonoscopy. Before colonoscopy, they are interviewed about taste, satisfaction and other side effects of laxative. During colonoscopy, two observers rated the colon- cleanliness score. In addition, the research assistant recorded the colonoscopy time, diagnosis and other procedure. After colonscopy, the patients are assessed for any complication or adverse reaction. The efficacies of laxatives are measured by the mean difference of colon-cleanliness score of each segment of colon. They are equivalent if the 95% confidence interval of the mean difference of all segments of colon lie within -1 to +1 and the mean score of all segments lie above 7. Result: The data are analyzed on intention-to-treat basis with different approach. The mean difference of colon-cleanliness score in rectum, sigmoid, descending 1 transverse colon and ascending colon & cecum between two groups are -0.29, -0.20, -0.17, 0.28 and 1.00 with the 95 % confidence interval - 0.97 to 0.39, - 0.92 to 0.52, - 1.02 to 0.69, - 0.61 to 1.17 and - 0.21 to 1.79 respectively . Three segments of colon are not lie within -1 to +1 and two segments are nearly lie outside this range. However nearly all segments have score above seven whatever the laxative is taken. The mean score of the taste and likeliness of senna and sodium phosphate are 8.6 (± 1.9), 8.3 (± 2.0) and 5.1 (± 2.8), 5.7 (± 2.9) respectively. The mean score of side effects such as nausea & vomiting, abdominal pain, vertigo and sleeplessness between these two groups are 0.9 (± 2.0), 1.3(± 2.3), 0.7 (+ 1.6), 1.2 (± 2.7) and 3.0 (± 3.5), 1.4(± 2.4), 1.3 (± 2.3), 1.4 (± 2.5) respectively. The adverse events, not related to laxatives, occurred in two patients from both groups. No patient is dead from those adverse events. Conclusion: There is no strong evidence to confirm that senna has equivalent efficacy as sodium phosphate solution in bowel preparation for colonoscopy, but it should be considered an alternative laxative.