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Is PEG (Polyethylene Glycol) a more effective laxative than Lactulose in the treatment of a child who is constipated?

Three Part Question

in a [child presenting with constipation] is a [Lactulose or PEG (Polyethylene Glycol)] more [effective as maintenance treatment after successful disimpaction]?

Clinical Scenario

A five year old child presents to the Emergency Department complaining of abdominal pains and not having passed a stool for at least two weeks. After an abdominal examination you diagnose faecal impaction. After the child has been successfully disimpacted, you are about to decide on the maintenance treatment you wonder whether there would be any difference in efficacy of the treatment if you used Movicol instead of Lactulose.

Search Strategy

Medline 1950- May 2007 and Embase 1980 to May 2007 using OVID interface. I also searched the Cochrane database and Cinahl
(Exp Constipation or or Exp fecal impaction or fece$.mp or faec$.mp or stool$.mp ) and ( osmotic adj or Exp Cathartics or laxative$.mp or ((Exp lactulose or and (Exp macrogol or Exp Polyethylene Glycol or limited to humans, English language and using a paediatrics filter.

Search Outcome

721 papers were found of which five were found to be relevant to the question. The rest of the papers were discarded.

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Candy DCA, et al
63 children aged between 2 and eleven diagnosed with faecal impaction. The trial had two phases the initial phase tested the efficacy and safety of PEG and E, the second tested the efficacy of PEG and E compared to Lactulose. In the second phase 28 were randomised to PEG and E and 30 to LactuloseRandomised Control TrialThe safety and efficacy of Polyethylene Glycol is tested by oral administration for up to seven days to all 63 children.58 (92%) of children achieved successful disimpaction. The median time for disimpaction was 6 daysThe trial doesn't compare the cathartics for their efficacy at disimpaction.
Daily assessments on number of successful defaecationsThe successful number of defaecations per week was higher for PEG and E (9.4) compared to (5.9) for Lactulose
Daily assessments on amount of medicine sachets takenThe mean was 0.91 for children taking PEG and E, the mean for Lactulose was 2.41
Daily assessments on use of senna as rescue treatmentAfter twelve weeks of treatment none of the children on PEG and E took senna, compared to 8 who were on Lactulose
If the children reimpacted after treatmentNone of the children on PEG and E reimpacted compared to seven who were on Lactulose
Rendeli C, et al
64 children with chronic neurogenic constipation completed the trial. Children with chronic neurogenic constipation randomised to either receive Lactulose or PEG 3350 for a period of six monthsRandomised Control TrialBowel frequency per week at one monthMean- 5.2 compared to 2.1 previously for PEG 3350, 3.1 compared to 2.2 previously for Lactulose. Constipation resolved in 46% of patients taking PEG 3350, compared to 26% taking LactuloseChildren had chronic neurogenic constipation. The trial was not blinded
Bowel frequency per week at six months5.1 in PEG 3350 group compared to 2.9 in the Lactulose group. Success rate of treatment 46% in PEG 3350 group compared to 22% in the Lactulose group
Side effectsNo significant side effects found in either group
Dupont C, et al
64 children with chronic neurogenic constipation completed the trial. Children with chronic neurogenic constipation randomised to either receive Lactulose or PEG 3350 for a period of six months 96 children aged between 6 months and 3 years 96 ambulatory constipated children treated for a period of 3 months with either lactulose or PEG in a double blind, double dummy RCT.Randomised Control TrialMean number of stools per week.In babies- PEG- 8.5, Lactulose-11, In toddlers, PEG-8, Lactulose-6, Results not significantThe trial wasn't strictly geared towards comparing efficacy of the different drugs and was more interested in finding out the tolerability of PEG.
Number of children experiencing hard stoolsAt day 42, PEG-9%, Lactulose-34%, Day 84 PEG-6%, Lactulose-28%
Presence of faecal impactionPEG- 2%, Lactulose-13%
Tolerance or each CatharticBoth treatments were well tolerated
Voskuijl W, et al
100 children aged between 6 months and 15 years with paediatric constipation. To compare the clinical efficacy and safety of PEG 3350 with lactuloseRandomised Control TrialFrequency of stools at week eightNo significant difference between treatments
Frequency of encopresis at week eightNo significant difference between treatments
Overall treatment success at week eightPEG-56% successfully treated, Lactulose- 29%
Adverse gastrointestinal eventsFewer side effects reported with PEG than Lactulose
After children on Lactulose switched to PEGThe success rate increased from 29% to 46% after 26 weeks of follow up
Gremse DA, et al
37 children aged between 2 and 16 yearsRandomised Control TrialNumber of patients medicine was effective inPEG 3350-84%, Lactulose-46%Small patient group There was no long term follow up of the patients, long term effects of the treatment was not recorded
Bowel frequency during 14 day treatment periodPEG 3350- 14.8, Lactulose-13.5
Colonic transit timeSignificantly shorter for PEG 3350
Stool consistencySimilar for both medications
Ease of stool passageSimilar for both medications


The commonest treatment options for constipation in children are Lactulose and PEG. The studies quite clearly show an advantage in the use of PEG over Lactulose. PEG has been shown to have fewer or similar amount of side effects as Lactulose. PEG has been shown to be a good choice for disimpaction and maintenance therapy after successful disimpaction. The trials show that patients on PEG have an increased bowel frequency than Lactulose. The trials also show that fewer patients reimpact whilst on PEG as maintenance therapy. The trials also show that PEG is a better treatment option even if the child doesn't have faecal impaction. Although the patient groups in the trials were a bit small a clear clinical advantage in the use of PEG over Lactulose has been found.

Clinical Bottom Line

In children who present with constipation with or without faecal impaction, PEG would be a better treatment than Lactulose.


  1. Candy DCA, et al Treatment of Faecal Impaction with Polyethelene Glycol Plus Electrolytes (PGE + E) Followed by a Double-blind Comparison of PEG + E Versus Lactulose as Maintenance Therapy Journal of Pediatric Gastroenterology & Nutrition. 43(1):65-70, 2006 Jul
  2. Rendeli C, et al, Polyethylene glycol 4000 vs. lactulose for the treatment of neurogenic constipation in myelomeningocele children: a randomized-controlled clinical trial Alimentary Pharmacology & Therapeutics 23(8):1259-65, 2006 Apr 15
  3. Dupont C, et al Double-blind randomized evaluation of clinical and biological tolerance of polyethylene glycol 4000 versus lactulose in constipated children Journal of Pediatric Gastroenterology & Nutrition 41(5):625-33, 2005 Nov
  4. Voskuijl W, et al, PEG 3350 (Transipeg) versus lactulose in the treatment of childhood functional constipation: a double blind, randomised, controlled, multicentre trial Gut 53(11):1590-4, 2004 Nov
  5. David A. Gremse, et al Comparison of Polyethylene Glycol 3350 Clin Pediatr 2002;