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In medicine, laxatives are "agents that produce a soft formed stool, and relax and loosen the bowels, typically used over a protracted period, to relieve constipation".[1]


Bulking agents

Example includes dietary fiber.

Osmotic laxatives

Osmotic laxatives
Laxative Dose How supplied Cost
Lactulose 10 grams 1419 ml of 10gm/15ml solution
(946 grams of lactulose)
(94.6 doses of 10 grams)
Magnesium hydroxide 2.4-4.8 grams    
Polyethylene glycol 17 grams 8.3 oz
(238 grams of polyethylene glycol)
(14 doses of 17 grams)
Sorbitol 13 grams 946 ml of 70% Solution
(662 gms of sorbitol)
(50 doses of 13 grams)

Osmotic laxatives include saline-based laxatives and poorly absorbed sugar laxatives.[2]

Poorly absorbed sugar laxatives

Polyethylene glycol 3350 (PEG 3350) contains glycols with molecular masses over 3000 which are poorly absorbed. It is available with or without electrolytes. Polyethylene glycol is better than lactulose according to the Cochrane Collaboration.[3] For adults, a randomized controlled trial found PEG [MiraLax or GlycoLax] 17 grams once per day better than tegaserod 6 mg twice per day.[4] A randomized controlled trial found greater improvement from initial 2 sachets (26 grams) of PEG with electrolytes versus 2 sachets (20 grams) of lactulose with option to change to 1 or 3 sachets [5]. 17 grams/day of PEG has been effective and safe in a randomized controlled trial for six months.[6] Another randomized controlled trial found no difference between sorbitol and lactulose [7].

For children, PEG was found to be more effective than lactulose.[8]


  1. Anonymous (2015), laxatives (English). Medical Subject Headings. U.S. National Library of Medicine.
  2. Lembo A, Camilleri M (October 2003). "Chronic constipation". N. Engl. J. Med. 349 (14): 1360–8. DOI:10.1056/NEJMra020995. PMID 14523145. Research Blogging.
  3. Lee-Robichaud H, Thomas K, Morgan J, Nelson RL (2010). "Lactulose versus Polyethylene Glycol for Chronic Constipation.". Cochrane Database Syst Rev 7: CD007570. DOI:10.1002/14651858.CD007570.pub2. PMID 20614462. Research Blogging.
  4. Di Palma JA, Cleveland MV, McGowan J, Herrera JL (2007). "A randomized, multicenter comparison of polyethylene glycol laxative and tegaserod in treatment of patients with chronic constipation". Am. J. Gastroenterol. 102 (9): 1964–71. DOI:10.1111/j.1572-0241.2007.01365.x. PMID 17573794. Research Blogging.
  5. Attar A, Lémann M, Ferguson A, Halphen M, Boutron M, Flourié B, Alix E, Salmeron M, Guillemot F, Chaussade S, Ménard A, Moreau J, Naudin G, Barthet M (1999). "Comparison of a low dose polyethylene glycol electrolyte solution with lactulose for treatment of chronic constipation.". Gut 44 (2): 226-30. PMID 9895382.
  6. Dipalma JA, Cleveland MV, McGowan J, Herrera JL (2007). "A randomized, multicenter, placebo-controlled trial of polyethylene glycol laxative for chronic treatment of chronic constipation". Am. J. Gastroenterol. 102 (7): 1436-41. DOI:10.1111/j.1572-0241.2007.01199.x. PMID 17403074. Research Blogging.
  7. Lederle F, Busch D, Mattox K, West M, Aske D (1990). "Cost-effective treatment of constipation in the elderly: a randomized double-blind comparison of sorbitol and lactulose.". Am J Med 89 (5): 597-601. DOI:10.1016/0002-9343(90)90177-F. PMID 2122724. Research Blogging.
  8. BestBETs: Is polyethylene glycol safe and effective for chro.... Retrieved on 2007-09-06.