The efficacy and safety of polyethylene glycol 3350 plus electrolytes (PEG+E) and ispaghula husk in the treatment of patients with chronic functional constipation were compared in a randomized-controlled, open-label, parallel group trial. 126 patients were randomized to treatment with PEG+E (13.8 g/sachet) twice-daily or ispaghula husk (3.5 g/sachet) dissolved in water twice-daily for 14 days; each intervention group had 63 patients. The weekly defecation rate and stool form as per the Bristol Stool chart were the primary end points. The time between the first dose of treatment and the first bowel movement was the secondary end point. 

The overall efficacy rate was 92% in PEG+E group compared to 73% in ispaghula husk group. 

The mean weekly defecation rate increased with both PEG+E and ispaghula husk; however, the increase was significantly greater with PEG+E, which increased the mean weekly defecation rate from 1.18 at baseline to 7.95 at Week 1 and 8.48 at Week 2. Conversely, the mean weekly defecation rate increased from 1.33 at baseline to 5.33 at Week 1 and to 5.71 at Week 2. At baseline, no patient included in the study had normal stool consistency. But at Week 1, 84.1% patients in the PEG+E group and 52.4% in the ispaghula group reported normal stool form. At Week 2, 87.3% in PEG+E group had normal stool consistence versus 66.7% in the ispaghula husk group. Patients treated with PEG+E had significantly shorter time to first defecation; almost half of the patients reported bowel movement within 24 hours and majority of the patients had a bowel movement by 48 hours of starting PEG+E. No between-group differences for adverse effects were noted. 

The study therefore concluded that PEG+E was more effective than ispaghula husk in relieving all the three symptoms of constipation chronic functional constipation - frequency of bowel movements, stool form and difficulty in defecation; it was also more rapid in its onset of action and was equally well-tolerated as ispaghula husk. 

Wang HJ, et al. Clin Drug Investig. 2004;24(10):569-76.