Reduction in Bowel Program Duration With Polyethylene Glycol Based Bisacodyl Suppositories Con't  Steven J. Stiens. MD

Fig 2-The time intervals 0f the BP studied were averaged and presented in minutes for PBG and HVB bisacodyl suppositories. The Time to Flatus was significantly longer after HVB suppository insertion. The Flatus to Stool flow period showed no significant difference between the agents. The Defecation Period was significantly shorter with use of the PGB suppository.

The mean BP interval that was most reduced was the Time To Flatus PGB 10 minutes vs. HVB 37 minutes) suggesting that the time difference may be caused by the rate and amount of bioavailability of the active ingredient in the suppositories bisacodyl). Water-miscible suppositories PGB) do not depend on body heat to melt and disperse after the phase change. Despite greater water solubility the PGB suppositor1es frequently did not completely dissolve by the time of stool flow. Bisacodyl. as compound of three benzene rings with hydroxyl groups, most likely acts more effectively as a solute in an ethylene glycol polymer base. This polar base may allow for quicker dispersion and greater potency of the bisacodyl on moist mucosal membranes.  

Although, a specific mechanism of action for bisacodyl on the gut has not been fully defined, this agent has been noted to be an effective gut evacuant in studies that have delivered bisacodyl to the intestinal mucosal surface.^9-12,4,13,6 When delivered to the colonic mucosal surface and observed with intraluminal electromyography, bisacodyl produces a complete suppression of rhythmic stationary activity and an increase in propagating sporadic spike bursts.⁴ This is consis tent with the increase in mass peristaltic waves observed in humans under fluoroscopy while adding a diphenylmethane- derived laxative to barium enemas.¹² Persons with SCI have been noted to have significantly more colonic spike wave activity in the basal unstimulated control state as compared with able-bodied controls.¹⁴ Despite the increased spike wave activity fecal retention usually occurs until reflex defecation is triggered mechanically or chemically. This in creased spike wave activity could represent excess segmental mixing of colonic contents. Bisacodyl therefore may suppress this activity and trigger a coordinated mass action for effective stool propulsion during defecation. 

The findings of this study show a small reduction in mean stool flow time HVB 31 minutes versus PGB

21 minutes without a significant difference in the number or digital stimulations required between the two groups This time reduction is consistent with other investigators' obser- vations. Oral bisacodyl tablets given before a nasogastnically presented lavage have sig- nificantly reduced the mean duration required for colonic cleansing.¹⁵ Ewe⁹ has noted an inverse linear relationship between the amount of bisacodyl delivered to the upper jejunum and gut transit time. It is possible that the shorter duration of stool flow time observed in this study is caused by properties of the PGB base that offer greater bisacodyl dispersion or better bioavailability. The unlikely possibility that the polyethylene glycol base itself acts as a gut stimulant was not explored. 

The decrease in the bowel program time noted by this study represents a clinically significant improvement over HVB suppositories for this Subject. The single subject design is particularly useful in showing differing efficiency between regimens for individual patients. Multiple single subject studies under similar conditions are required to estcblish generalizability of conclusions derived with individual sub jects. Expanded studies of the effects of PGB bisacodyl suppositories on BPs after spinal cord injury are currently in progress. 

Acknowledgment: Statistical analysis was performed through the consultative help of Jane C. Johnson. BA. at the Medical Informatics Group Biostatistics UMC School of Medicine. University of Missouri, Columbia, MO. The following colleagues critically reviewed the manuscript and are a continued source of beneficial advice Margaret Hammond, St D Richard Buhrer, RN, MN. and Victoria Bozzacco. MN I also thank other members of the Seattle VAMC SCI Gastrointestinal study group for their commitment to neurogenic bowel research: Janet Loehr. ARNP. Catherine O'Keefe, RN. BSN, and Glen House, MSIV Thanks to Paula Micklesen, BS. for her perceptive graphic summary of the bowel intervals  and experimental results and to Debra Roberts for her organization and attentiveness to the word processing as the manuscript developed,  

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