Tolerance and long-term efficacy of polyethylene glycol 4000 (Forlax®) compared to lactulose in elderly patients with chronic constipation

To assess the tolerance and potential nutritional consequences of long-term repeated doses of PEG 4000 (10 to 30 g/day) in elderly patients with chronic constipation as compared to lactulose (10-30 g/ day).

Single blind, randomised, multicentre, parallel group comparative study.

Community-dwelling patients and nursing homes residents aged 70 years and older with a history of chronic constipation.

PEG 4000 (10-30 g/day) or lactulose (10-30 g/day) for six months.

Clinical nutritional status (Mini Nutritional Assessment), blood and stool samples were taken at baseline and after three and six months for assay of nutritional and absorption parameters. A patient diary documented digestive symptoms and adverse events were recorded. Information on efficacy (stool frequency and consistency) was collected as a secondary outcome measure.

Of the 316 patients screened, 245 eligible patients constituted the ITT population (PEG 4000: N = 118; lactulose group: N = 127). The proportion of patients receiving PEG 4000 with abnormal levels of electrolytes, nutritional markers or vitamins did not significantly change in the six months after initiating laxative treatment and do not differ between the two groups. After a D-xylose challenge test, the proportion of patients with abnormally low xylosaemia (suggesting malabsorption) varied from 24.6% at baseline to 35.8% after six months in the PEG 4000 group and from 29.1% to 42.4% in the lactulose group, with no significant between-group or within-group differences. The proportion of patients with poor nutritional status (MNA score <17) varied from 8.5% at baseline to 9.8% after 6 months in the PEG 4000 group and from 3.9% to 5.0% in the lactulose group. No changes in stool fat or total or soluble stool nitrogen were observed in the minority of patients for whom stool analysis was performed. A significantly higher stool frequency p <0.05) and improved stool consistency p <0.05) was observed in the PEG 4000 group compared to the lactulose group at each monthly evaluation period.

After six months of treatment with PEG 4000, no clinically relevant changes in biochemical and nutritional parameters and no unanticipated treatment-related adverse events were detected, demonstrating the good clinical tolerance of PEG 4000 in this population of elderly constipated patients. This tolerance was associated with a better clinical efficacy of PEG 4000 compared to lactulose.