Attar, A., Lemann, M., Ferguson, A., Halphen, M., Boutron, M.C., Flourie, B., . . . Barthet, M. (1999). Comparison of a low dose polyethylene glycol electrolyte solution with lactulose for treatment of chronic constipation. Gut, 44, 226–230.

In part A, patients were randomized to receive either PEG plus electrolytes (PEG+E) (n = 60) or lactulose (n = 55) for one month. In part B, 65 patients continued on the treatment for another two months. Patients received PEG+E, irrespective of the laxative they received at the start of part A.

PEG 3350 is an osmotic laxative that opposes the colon’s normal drying action on the feces. The increasing fecal bulk stretches the circular muscle fibers in the bowel wall and triggers myogenic peristalsis. PEG+E provides electrolyte depletion and dehydration that can occur with other laxatives.

Lactulose is metabolized to lactic acid by bacteria in the colon. Those bacteria exert a local osmotic effect, drawing water and electrolytes into the colon from the surrounding tissues to bulk feces.

• The study reported on a sample of 115 patients.
• Patients were included in the study if they were aged 18 to 90 years and had fewer than three stools a week and/or difficult evacuation for at least three months.
• Patients were excluded if they had secondary constipation; were taking concomitant medication that might modify bowel transit; had severe liver, renal, or cardiac impairment; were not likely to comply with treatment; were not able to give informed consent, or were women of childbearing age not using effective contraception.

This was a single-blind, randomized, multicenter study.

The efficacy of PEG+E was evaluated by

• Number of stools per day
• Evacuation score
• Dyschezia index (graded from 0-3)
• Global satisfaction index (analog scale from 0-10)

Part A

• At the end of the one-month period, PEG+E showed consistently and significantly better results in number of stools per day, ease of evacuation, and global satisfaction.
• Sixty percent of PEG+E recipients did not use all their sachets, compared with 40% in the lactulose group.
• In the lactulose group, 23% increased their dosage to three or more sachets per day, whereas 64% of lactulose recipients used two to three sachets per day.
• The use of suppositories and micro-enemas was significantly lower in the PEG+E group than the lactulose group (16% versus 34%).

Part B

• Daily dosage of PEG+E remained stable, with most patients using one to two sachets per day.
• Patients in the lactulose group tended to increase to three sachets per day.
• At the end of three months, the efficacy of PEG+E was significantly better than that produced by lactulose in number of stools per day and ease of evacuation.

Use of PEG+E instead of lactulose doubled the percentage of patients successfully treated at three months. PEG+E was found to be a superior treatment compared to lactulose to treat idiopathic constipation. The study was well designed.