Polyethylene glycol (PEG) 3350 is a non-absorbable, nonmetabolized osmotic agent used in lavage solutions for gut cleansing. A total of 115 patients of 70:30 general:geriatric ratio with chronic constipation entered a multicenter, randomized, comparative trial. They initially received two sachets containing either PEG (13 g/sachet) or lactulose (10 g/sachet) and were given an option to change the dose to one or three sachets/day, depending on response. Ninety nine patients completed the trial. After four weeks, patients in the PEG group (n=50) had a higher number of stools and a lower median daily score for straining at stool than patients in the lactulose group (n=49). The mean stool frequency was higher in the PEG than in the lactulose group and straining at stool was higher in the PEG than in the lactulose group. As lactulose is metabolized by the colonic bacterial flora to produce short chain fatty acids, it is expected that its laxative effect would be associated with a prominent formation of gases including carbon dioxide, methane, and hydrogen. Most of the common side effects ascribed to lactulose was abdominal pain, bloating, and flatus. Overall improvement was greater in the PEG group. But, the mean number of liquid stools was higher in the PEG group but significant difference was there only for the first two weeks. There were no serious adverse events and no significant change in other laboratory parameters in any group. At the end of the study, the present study concluded that PEG 3350 at low daily doses (13–39 g/day) was more efficient and better tolerated than lactulose (10–30 g/day) in the treatment of chronic idiopathic constipation. Low dose PEG may be considered as a better alternative in patients with constipation obstinate to more conventional and less costly treatments. There was no serious toxicity event of PEG after three months of treatment. The optimal dosage recommendation was between 13 and 26 g of PEG per day in most of the patients.

Source: Attar A, Lémann M, Ferguson A, et al. Gut 1999;44:226-230