A meta-analysis was conducted to review available literature to compare the effectiveness of polyethylene glycol (PEG) and lactulose in the treatment of patients with chronic constipation and fecal impaction. The findings of this meta-analysis were published in April 2011 in The Cochrane Database of Systematic Reviews. MEDLINE, EMBASE and CINAHL databases, and the Cochrane Central Register of Controlled Trials were searched for randomized-controlled trials that compared use of two commonly used osmotic laxatives, lactulose and PEG, in the management of chronic constipation. One hundred and three studies were identified; of these, 10 (Candy 2006, Rendeli 2006, Dupont 2005, Brandt 2005, Fritz 2005, Voskuijl 2004, Bouhnik 2004, Guest 2004, Gremse 2002, Christie 2002, Mangin 2002, Attar 1999, Ferguson 1999, Freedman 1997) met the inclusion criteria and were included in this meta-analysis. These 10 trials were conducted between 1997 and 2007 in six different countries and together enrolled 868 subjects (322 adults and 546 children) with age ranging from 3 months to 70 years. The primary outcome measure was the change in frequency of defecation. The secondary outcome measures were the use of additional products (e.g. alternative laxative agents, enemas), percentage in global improvement of symptoms and relief of abdominal pain.

• Five trials (Attar 1999, Bouhnik 2004, Candy 2006, Gremse 2002, Voskuijl 2004) reported stool frequency per week; all showed that treatment with PEG resulted in a higher stool frequency per week versus lactulose.
• Two trials (Wang 2007, Zhang 2003) reported stool form on the Bristol Stool chart; a higher Bristol Stool Score (softer stool) was noted with PEG versus lactulose.
• Three trials (Bouhnik 2004, Dupont 2005, Wang 2007) reported relief of abdominal pain; of these, two trials (Dupont 2005, Wang 2007) showed favorable results with PEG, while one trial (Bouhnik 2004) reported comparable outcomes with PEG and lactulose.
• Three trials (Attar 1999, Candy 2006, Dupont 2005) compared the use of additional products in the two treatment groups. Compared to lactulose treated group, patients in the PEG treatment group required less use of additional products to relieve their constipation.

The results of the studies included in the meta-analysis showed that PEG had better outcomes than lactulose with regard to stool frequency per week, form of stool, relief of abdominal pain and the need for additional products. Subgroup analysis showed that while PEG was better than lactulose for relief of abdominal pain in children, both PEG and lactulose had comparable effects for relief of abdominal pain in adults. Based on these findings, the review concluded that that PEG should be preferred over lactulose when treating chronic constipation.

Lee-Robichaud H, et al. Cochrane Database Syst Rev 2010;(7):CD00757