Lee-Robichaud, H., Thomas, K., Morgan, J., & Nelson, R.L. (2010). Lactulose versus polyethylene glycol for chronic constipation. Cochrane Database of Systematic Reviews, 7, CD007570.

To identify and review all relevant data to determine whether lactulose or polyethylene glycol (PEG) is more effective in treating chronic constipation.

Databases searched were Medline, Embase, CINAHL, and the Cochrane Central Register of Controlled Trials. Bibliographies of studies and conference proceedings  were hand searched.

Search keywords were fecal impaction, chronic constipation, delayed bowel movement, obstipation, irregularity, polyethylene glycol, ethylene glycol, PEG, ethylene oxide, PEG 3350, lactulose, and disaccharide.

Studies were included in the review if they

• Were randomized controlled trials comparing the use of lactulose and PEG
• Reported on adult patients or children diagnosed with chronic constipation or fecal impaction.

One hundred three initial references to January 24, 2008, were identified. A final set of 10 trials was included in this review. Studies were evaluated for various sources of bias and overall methodological quality. Trials were conducted in different countries in a variety of settings.

• The 10 trials included a total of 868 participants.
• 322 were adults and 546 were children.

• In most studies, assessment of study quality by investigators yielded highly variable results and little agreement of bias issues.
• In five studies, the overall mean difference in stool frequency per week was 0.65 (95% confidence interval [CI] [0.15, 1.15], p = 0.01) in favor of PEG.
• Among three studies in children, the mean difference in stool frequency per week was 1.57 (95% CI [0.36, 2.77], p = 0.011) in favor of PEG.
• In two studies that measured stool form and consistency, the mean difference was 0.89 (95% CI [0.43, 1.45], p = 0.00015) in favor of PEG.
• In one study of adults and two studies in children, the odds ratio for relief of abdominal pain was 2.09 (95% CI [1.26, 3.44], p = 0.004) in favor of PEG.
• Across three studies, patients on PEG had much less need for additional products to manage constipation (p = 0.000078).

• Findings suggest that PEG may be more useful than lactulose in both children and adults for improvement in constipation; however, the evidence is insufficient to draw firm conclusions because of the small number of studies and degree of heterogeneity found.
• Studies had a number of methodological issues.
• This review involved studies that did not include an oncology population.

One study included a sample of patients on methadone maintenance, which may have some relevance for constipation associated with opioid use.