Direct Comparison Favors Electrolyte Bowel Prep

CHICAGO — For bowel cleanliness and readiness, polyethylene glycol is better than a combination of sodium picosulfate plus magnesium citrate, and split dosing over 2 days is more effective than split dosing over 1 day, according to a new study.

"Two-day split dosing will result in superiority of visualization of the bowel," said investigator Kirles Bishay, MD, from the University of Ottawa in Ontario, Canada. This has the potential to reduce the rate of missed adenomas and the need for repeat colonoscopy, he told Medscape Medical News.

In their study, Dr Bishay and his colleagues assessed 141 patients scheduled to undergo outpatient colonoscopy at the Forzani & MacPhail Colon Cancer Screening Centre at the University of Calgary in Alberta, Canada.

They randomly assigned 70 patients to bowel prep with polyethylene glycol (GoLYTELY) and 71 patients to the combination of sodium picosulfate plus magnesium citrate (Picolax). The groups were well matched for sex and age.

Endoscopists were blinded to the bowel preparation.

Patients with appointments before 10 AM used the 1-day split-dose method, and took both doses of bowel prep the day before the procedure. Patients with afternoon appointments used the 2-day split-dose method, and took one dose the night before the procedure and the second in the morning, 5 to 6 hours before the procedure.

The standard, validated Ottawa Bowel Preparation Score was used to assess the degree of bowel readiness.

"Regardless of whether patients were assigned to a 1- or 2-day split," polyethylene glycol was superior to the combination, Dr Bishay reported during a poster presentation here at Digestive Disease Week 2017.

Mean Ottawa score, indicating bowel cleanliness, was better with polyethylene glycol than with the combination (4.14 vs 5.11; P = .019). And the rate of prep considered adequate was higher with polyethylene glycol (80% vs 60%; P = .007).

And "regardless of what agent you got," the 2-day split was significantly better than the 1-day split, he added.

The mean Ottawa score was better with 2-day than with 1-day split dosing (3.68 vs 5.69; P < .001). And visualization of the right colon was better with 2-day split dosing (1.27 vs 2.10; P < .001).

Conflicting Results in the Literature

These findings support those from a meta-analysis of split dosing (Gastroenterology. 2015;149:79-88), which was "very much in favor of the 2-day split," Dr Bishay reported.

However, in another meta-analysis (Eur J Clin Pharmacol. 2016;72:523-532), no difference was demonstrated, although there was a trend toward better prep with propylene glycol than with the combination. But that analysis was heterogeneous, including both single-dose and split-dose regimens, "which may have had an effect," he pointed out.

Traditional standard bowel preparation required patients to consume 4 L of propylene glycol in one dose the day before their procedure. This volume can create a sense of fullness and cramping in some patients, and typically 5% to 15% of patients are unable to drink the entire amount, said Subhas Banerjee, MD, from Stanford University in California. The sodium picosulfate plus magnesium citrate combination is a newer, 'low-volume' bowel prep, and is typically administered as a 2 L dose.

In this study, Dr Bishay's team "found that PEG does work better than a low-dose prep, and that a 2-day split works better than a 1-day split, particularly for the right side of the colon, a location where subtle flat polyps are more common and a good cleanout is essential for detection of these," Dr Banerjee told by Medscape Medical News.

"Essentially, a 2-day split prep using PEG provides the best bowel cleanout, despite its disadvantages: a larger volume to drink and the need for early morning colonoscopy patients to wake up early to complete their consumption of the bowel prep," he said.

In general, "the split dose is easier for patients to tolerate because they only need to drink half the volume, can take a break for several hours to recover, then drink the other half," Dr Banerjee explained. The split-dose strategy generally results in a higher quality of cleanout and a higher quality of colonoscopy examination. "Given the superior cleanout, potentially more polyps may be seen and removed during colonoscopy," he added.

However, even with split-dosing, the second dose must be consumed starting approximately 6 hours before the procedure. "This creates practical problems for patients who have an early morning procedure. If the procedure is at 7:30 AM, the patient would have to wake up around 1:00 AM to start drinking the second half of the bowel prep," he pointed out.

Dr Bishay and Dr Banerjee have disclosed no relevant financial relationships.

Digestive Disease Week (DDW) 2017: Abstract Sa1068. Presented May 6, 2017.


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Direct Comparison Favors Electrolyte Bowel Prep. Medscape. May 16, 2017.

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