Comparison of polyethylene glycol with and without electrolytes in the treatment of constipation in elderly institutionalized patients: a randomized, double-blind, parallel-group study.

backgroundPolyethylene glycol (PEG) is a commonly used osmotic laxative. PEG with electrolytes is mixed with water, but PEG without electrolytes can also be mixed with, for example, juice, coffee or tea, making it more palatable. Laxatives, including PEG, are commonly used by the elderly, particularly those living in institutions. Few clinical studies, however, have investigated the use of PEG in this population.

objectiveTo test whether PEG 4000 without electrolytes (hypotonic PEG) is at least as effective and safe as PEG 4000 with electrolytes (isotonic PEG) in elderly institutionalized constipated patients. The acceptability of the treatments was also compared.

methodsThis randomized, double-blind, parallel-group study was conducted at ten private assisted-living facilities or communal nursing homes in Finland. Eligible patients were required to have used isotonic PEG at a stable dose without any other treatment for constipation (except for Plantago ovata seeds) for at least 2 weeks prior to a run-in period. After the 1-week run-in, 62 patients (mean age 86 years; range 66-99 years) were randomly either switched to receive hypotonic PEG or continued to receive isotonic PEG, both dissolved in water, 12 g once or twice daily or once every other day, for 4 weeks. Stool frequency, stool consistency, stool straining and gastrointestinal symptoms were recorded. Safety laboratory tests were conducted before and after the treatment period. Acceptability was assessed at the end of the study.

resultsAt week 4, mean (SD) weekly stool frequencies in the hypotonic and isotonic PEG groups were 8.5 (4.5) and 8.4 (3.6), respectively. The mean stool frequency ratio (95% CI) was 0.90 (0.74, 1.10); thus, the PEG products were considered equally effective. At week 4, the proportion of patients with soft or normal stool consistency was higher in the hypotonic PEG group than in the isotonic PEG group (70% vs 52%), but this difference was not statistically significant. There were no differences between the groups in stool straining or gastrointestinal symptoms. In the safety laboratory tests, no clinically significant differences between the groups were detected, although plasma sodium level was statistically significantly lower in the hypotonic PEG group at the end of the study (137.7 vs 138.9 mmol/L, respectively; p = 0.012). Most patients were willing to continue their study treatment (85% in the hypotonic PEG and 63% in the isotonic PEG group; p = 0.070). Compared with only 12% of the patients receiving hypotonic PEG, however, 31% of the patients in the isotonic PEG group rated the taste of the study treatment as bad or very bad (p = 0.101).

conclusionHypotonic PEG solution is as effective as isotonic PEG in the treatment of constipation in elderly institutionalized patients. Both treatments appear safe, well tolerated and, when dissolved in water, well accepted by the majority of the patients. When desired, switching from isotonic to hypotonic PEG can safely take place in elderly individuals without compromising efficacy.