Chronic constipation is a common problem. Patients, including physicians, perceive constipation in different ways; hence, prevalence rates vary. Non-organic constipation is constipation with no underlying medical cause. Initial management of constipation comprises of treatment of underlying etiology (if present) along with recommendations for adequate amounts of dietary fiber and fluids and increasing physical activity. The next step in management involves laxatives (osmotic, bulk and stimulant). Polyethylene glycol (PEG) with/without electrolytes and lactulose are the commonly prescribed osmotic laxatives.

A systematic review and meta-analysis was conducted to compare the efficacy of PEG versus placebo or active comparators such as lactulose, for the treatment of non-organic constipation in adults. MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Clinical Trials and Google Scholar databases were searched for published randomized controlled trials or trials with parallel-group or cross-over design of PEG in adults with constipation published in peer-reviewed journals from January 1970 to October 2009. Studies that reported about frequency of defecation were eligible for inclusion in the meta-analysis. Patients who had a primary bowel disease like irritable bowel syndrome, Hirschsprung’s disease, as the cause of constipation were not included in the study. Twenty studies were included in the meta-analysis; of these, 10 studies compared PEG with placebo, seven with lactulose and four with other agents such as ispaghula. 

A significant improvement in constipation was observed in the comparative studies of PEG vs placebo and lactulose. The number of mean defecations per week significantly increased with PEG compared with placebo (standard mean differences [SMD] 1.98, 95% CI 1.16 to 2.81; 10 studies) and lactulose (SMD 1.01, 95% CI 0.41 to 1.62, I2=53.5%; seven studies). PEG had good tolerability in the placebo studies. In the trials comparing PEG with lactulose, the incidence of adverse events with PEG was 6-16% vs 10-24% with lactulose. 

This meta-analysis compared PEG with placebo and lactulose and found that PEG was regarded as a more effective laxative, compared to lactulose, in adults with non-organic constipation by both investigators and patients. 

Belsey JD, et al. Int J Clin Pract. 2010 Jun;64(7):944-55.