Polyethylene glycol should be the preferred laxative rather than lactulose for the treatment of patients with chronic constipation, according to a meta-analysis published in the Cochrane Database of Systematic Reviews. MEDLINE, EMBASE and CINAHL databases, and the Cochrane Central Register of Controlled Trials were searched to identify RCTs comparing lactulose and polyethylene glycol in the management of fecal impaction and chronic constipation; 10 trials involving 868 participants (Candy 2006, Rendeli 2006, Dupont 2005, Wang 2007, Zhang 2003, Voskuijl 2004, Bouhnik 2004, Gremse 2002, Attar 1999, Freedman 1997), published between 1997 and 2007, met the selection criteria and were reviewed in the meta-analysis. Change in frequency of defecation was selected as the primary outcome measure; the secondary outcomes included 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) showed a higher weekly stool frequency with PEG versus lactulose. Evaluation of stool form identified two trials (Wang 2007, Zhang 2003) that reported a higher Bristol Stool score (softer stool) with the use of PEG compared with lactulose. Two trials (Dupont 2005, Wang 2007) showed better relief of abdominal pain with PEG than with lactulose. In one trial (Bouhnik 2004), lactulose and PEG had similar effects. Compared to patients treated with lactulose, those managed with PEG needed fewer additional products to alleviate constipation as reported in three trials (Attar 1999, Candy 2006, Dupont 2005)

These trials showed that PEG was more effective than lactulose relating to stool frequency per week, stool form, relief of abdominal pain and need for additional products. The review therefore concluded that PEG should be preferred over lactulose when treating chronic constipation. PEG was effective in both adults and children.

Source: Lee-Robichaud H, et al. Cochrane Database Syst Rev. 2010;(7):CD007570