Pharmacologically Initiated Defecation for Persons With Spinal Cord Injury: Effectiveness of Three Agents

J. Glen House, MD, Steven A. Stiens, MD

Objective: To compare the effectiveness of hydrogenated vegetable oil-based bisacodyl (HVB) suppositories, polyethylene glycol-based bisocodyl (PGB) suppositories, and polyethylene glycol- based, glycerine, docusate sodium mini-enemas (TVC) in subjects with upper motor neuron spinal cord lesions.

Study Design: Prospective randomized double blind. Fifteen subjects received one of three HVB and 3 PGB suppositories in randomized sequence for each of six scheduled bowel care sessions. Additionally, 10 subjects received 3 TVC. The analysis used time events that divided the bowel sessions into intervals. The analysis also compared digital simulations, incontinence, and quantity of stool. Wilcoxon rank sum tests and paired t tests were used to compare the means of intervals during bowel care initiated by HVB, PGB, and TVC.

Results: (means in minutes and p values): Time to Flatus – HVB,32; PGB, 15; TVC, 15; p <.026, HVB-PGB; p < .983, PGB-TVC; Flatus to Stool Flow - HVB, 6.7 ; PGB 5.5; TVC 3.9 p < .672, HVB - PGB; p < .068, PGB-TVC; Defecation Period - HVB , 36; PGB, 20; TVC, 17; p < .037, HVB - PGB; p < .479, PGB - TVC; Wait Until Transfer - HVB, 10.9; PGB, 10.7; TVC, 7.4; p < .932, HVB - PGB; p < .043, PGB - TVC; Total Time for the bowel program -HVB, 74.5; PGB, 43; TVC, 37; p < .010, HVB - PGB; p < .458, PGB - TVC; percent incidence of incontinence between bowel care sessions - HVB, .067; PGB, .067; TVC, .033; p < 1.0, HBV-PGB; p < .678, PGB-TVC; amount of stool produced - HVB, 3.30; PGB, 3.49; TVC, 3.38; p < .276, HVB-PGB; p < .630, PGB-TVC; average number of digital stimulations per bowel care procedure -HVB, 4.4; PGB, 4.1; TVC, 3.8; p < .411, HVB-PGB; p < .293, PGB-TVC; time per digital stimulation in seconds - HVB 107; PGB, 40; TVC, 83; p < .149, HVB-PGB; p < .352 PGB-TVC; and the total time, in minutes spent performing digital stimulation during bowel care -HVB, 10.0; PGB, 2.7; TVC, 5.9; p <.151, HVB-PGB; p <.325, PGB-TVC.

Conclusion: Bowel care took less time when initiated with the PGB bisacodyl or TVC mini-enema as compared with the HVB bisacodyl suppository (p < .01)

This is a US government work. There are no restrictions on its use.


From the Department of Physical Medicine and Rehabilitation Baylor College of Medicine, Houston TX. and University of Washington School of Medicine Seattle (Dr. House) and the Spinal Cord Injury Unit, Veterans Administration Puget Sound Health Care System, Seattle Division, and Department of Rehabilitation Medicine, University of Washington, Seattle (Dr.Stiens).

Submitted for publication November 6,1997. Accepted in revised form January29,1997 No commercial party having direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated.

Reprint requests to Steven A. Stiens MD. MS. Mail Location 356-490 Health Sciences Building BB938. 1959 NE Pacific, Seattle, WA. 98195. This is a US Government work. There are no restrictions on its use. 0003-9993/97/7810-4263 $0.00/0

Spinal Cord Injury (SCI) results in many impairments that profoundly affect a person’s life. Neurongenic bowel dysfunction is one of the most significant complications that affects the quality of life. Furthermore, bowel care often occupies a relatively large portion of the day for a person with SCI. More than 20% of persons with SCI report difficulty with evacuation of their bowels. Bowel care procedures can require up to 3 hours for completion, and yet yield insufficient results. Complications related to bowel dysfunctioncan lead to patient morbidity and require surgical intervention. Fecal impaction is the most common colonic complication after SCI, but complications also include intractable constipation and overflow incontinence. Bowel dysfunction continues to be a major cause of autonomic dysreflexia after SCI. Chronic complications, such as diverticuli, develop more rapidly after SCI but rarely occur before 5 years after injury and are assumed to be acquired. It has been suggested that appropriate bowel program management to prevent chronic rectal overdistension may postponeor prevent these complications. After SCI, volitional defecation is disrupted and a bowel program that includes scheduled bowel care sessions is often required to achieve predictable defecation, continence of stool, and prevention of complications. Several techniques are used to initiate defecation, such as rectal insertion of suppositories, mini-enemas, enemas, and digital stimulation.

Individuals with SCI occasionally attempt to augment their bowel programs with laxatives. Oral laxatives have been categorized into four groups; dietary fiber and bulking agents, osmotic laxatives, stimulant laxatives and stool softeners. Bulking agents (bran, wheat husk, etc) cause fluid retention within the colon and increase bulk and stool softeners, leading to facilitated intestinal transit. Osmotic laxatives (mannitol, sorbitol, lactulose, magnesium citrate) retain water in the feces to produce a consistency that facilitates transit. Stimulant laxatives (bisacodyl, phennolphthanalein, glycerol) act at the intestinal mucosa and stimulate intestinal motility, which decreases the time available for salt and water absorption, further decreasing transit time. Stool softeners (docusate sodium, etc.) directly decrease stool firmness, reducing constipation. Suppositories frequently contain a contact stimulant laxative and are administrated to enhance colonic peristalsis. Currently, bisacodyl is the active ingredients in most commonly used in bowel evacuation suppositories. Bisacodyl (bis (p-acetoxyphenal)-2-pyridyl- methane), is a compound that is practically insoluble in water and alkaline solutions. This agent is very poorly absorbed by the colon and acts directly at the mucosa to stimulate the sensory nerves, producing a parasympathetic relex response of increased peristalic contractions throughout the large intestine. A rectally-administered water suspension of bisacodyl produces increased peristaltic activity in 3 minutes. Bisacodyl also stimulates fluid and electrolyte accumulation within the colon, adding laxative affects.

The most commonly used laxative suppositories contain 10mg bisacodyl powder distributed within a hydrogenated vegetable-oil based (HVB). A considerably long waiting period has been observed after insertion of the HVB suppository until initial results of flatus and first stool flow. Studies have found that up to 20% of patients require at least 45 minutes from HVB insertion to first stool flow and may experience excessive mucus production after the completion of the bowel care, as well as stool incontinence. A water-miscible, bisacodyl-containing suppository compounded with a polyethylene glycol base (PGB) that has recently become available has been anecdotally reported to decrease overall bowel care time. Previously, a single subject study completed at this institution and an unblinded trial at the Tampa (FL) Veteran’s Medical Center suggested a clinically significant decrease in bowel care time using the PGB suppository.

Mini-enemas are an increasingly popular method of administration of stimulant laxatives for the initiation of bowel care. The Theravac SB mini-enenma (TVC) is a small soft plastic ampule with a 3cm extended tip that is inserted into the rectum after its distal end is cut off or puntured; the bulb is squeezed and its contents enter the rectum, acting on the mucosa as a surface stimulant within minutes. TVC contains a 4ml liquid combination of glycerine (275mg) and docusate sodium (283mg) in a polyethylene base.

This randomized, prospective, double-blind study was designed to compare the effectiveness of bowel care using bisacodyl suppositories compounded with HVB and PGB. Additionally, the PGB suppository and the TVC mini-enema were compared independently.


The study design and objectives were approved by the Intradepartmental Scientific Merit Review and University Human Subjects Committees. Subjects were recruited from an inpatient SCI unit at a VA Health Care System Division, and participated after signed concent. Inclusion criteria included: 3 months or longer since the SCI, spinal cord lesions above the 12th thoracic neurological level, lack of anal sensation, lack of voluntary anal sphincter contraction, a stable bowel program with pharmacologically-triggered bowel care, and the absence of known gastrointestinal disease. Subject history was reviewed for consistency in bowel care. Chart review identified lesion level, sensory and motor performance, anal cutaneous reflex, bulbocavernousos relex and lower extremity phasic stretch reflexes.

The two types of bisacodyl suppositories used in the study differ only in the base used for dispersion of the active ingredient. The HVB suppositoriesa contained 10mg bisacodyl USPin a hydrogenated vegetable- oil base. The PGB suppositoriesb contained 10mg bisacodyl dissolved in a mixed polyethylene glycol polymer base of two molecular weights: E1450 and E400

A randomized, prospective, double-blind study was implemented. Each subject was designated a previously determined ramdomized sequence of six suppositories to study three HVB and three PGB suppositories known only to the pharmacy. Time events and data were collected for three bowel care sessions in 10 subjects, who normally use Theravac SB mini-enemac after completing the suppository study. The investigators, nurses, and subjects were unaware of each individual’s randomized sequence. Pharmacy personnel possessed the only suppository sequence and dispensed the subjects predetermined suppository blindly to the nursing staff. The nurses then administered the suppository to the subject and recorded timed bowel care events.

Bowel care was performed using a consistent protocol. Subjects were either seated upright or lying on their side (left or right specified) during bowel program. This position remained unchanged for each subject throughout the study and was consistent with usual bowel care session , either a 10mg HVB or 10mg PGB suppository was inserted half a finger’s length through the anal sphincter and placed against the mucosal surface of the rectal wall. Theravac SB mini-enema tips were cut off and 3cm extension was inserted into the rectum with bulb remaining outside. The bulb was then squeezed by the patient or the nurse if the patient did not have the required dexterity. The time of insertion of the suppository or squeeze of the Theravac SB contents into the rectum was considered 0 time and progress of bowel care was documented with time parameters. Digital stimulation and/or manual evacuation was not performed during suppository insertion, but was allowed only after either first flatus or first stool flow. The bowel care period was divided into intervals by discrete events. First Flatus marks the end of the interval from insertion of suppository until the first gas is passed, Begin Stool Flow marks the beginning of the defecation interval, End Stool Flow marks the end of the defecation interval, Time Off Toilet marks the interval from last stool flow to transfer off toilet or completion of clean-up if in bed, Total Time marks the time from insertion of the suppository to the last stool flow. Both duration and frequency of digital stimulation and manual evacuation were recorded. Stool results were recorded as: 0, none; 1, minimal; 2,small; 3, moderate; 4, large; 5, very large. All episodes of incontinence were recorded and defined as any passage of substance through the anus (include stool, mucus, liquid, etc.) at ant time outside the designated bowel care proceedure.

Statistical analysis. Continuous mean interval data were compared using paired t tests. Ordinary data were compared with Wilcoxon rank sum tests. Probability (p) values were derived taking .05 as the level of significance.


The subject demographics include nine cervical and six thoracic level injuries. Of the 15 subjects, 11 were complete and 4 were incomplete spinal cord lesions. All patients had a positive anal cutaneous reflex and bulbocavenousus relex and normal to hyperreflexic lower extremity phasic stretch reflexes to tendon percussion. The 15 subjects had a mean age of 45 years (range, 26 to 61), were between 3 months and 45 years postinjury, and had been admitted to a VA Medical Center SCI unit for reasons unrelated to gastrointestinal pathology.

One hundred fourteen bowel care sessions were studied from the 15 subjects:43 using PGB suppositories, 43 using HVB suppositories and 28 using TVC. No subjects reported gastrointestinal symptoms or autonomic dysreflexia during or around the time of the bowel care. There were 10 incontinence episodes reported. Ten occurred within 1 hour of the end of the bowel care, 3 after PGB, 5 after HVB and 2 after TVC. Two of the 5 HVB incontinence episodes occurred on the same day in one subject, separated by a 2-hour period.

Therefore, to prevent gastrointestinal complications that can occur due to fecal distention of the colon, a bisacodyl