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Classification: B

Drug products: Forlax, Forlax Junior, Forlax®, Forlax® Junior, Olopeg, Omnilax

ATC code: A06AD15

Substances: macrogol


Controlled studies on differences between men and women in polyethylene glycol efficacy and safety are lacking. Pharmacokinetic studies have not shown any large differences between men and women.

Additional information

Macrogol is also known as polyethylene glycol (PEG) and is used as in treatment of obstipation and in bowel cleansing prior to colonoscopy.

Pharmacokinetics and dosing

The effect of patient's sex on the pharmacokinetics of PEG 3350 has been evaluated in a multiple-dose administration of 17 g PEG 3350 one daily for 7 days in healthy volunteers (7 men, 7 women). In the young age group (18-40 years), Cmax was almost twice as high in women than in men (8.87 vs 4.51 ng/ml/kg). However, due to a small sample size and high variability, confidence intervals were very wide. The authors suggest that overall, patient's sex did not alter the pharmacokinetics [3]. No studies with a clinically relevant sex analysis regarding the dosing of PEG have been found.


Several studies have shown that patient's sex have no effect on the cleansing of the bowel when using PEG-electrolyte solution as bowel preparation [4-6].

Adverse effects

The tolerability of the three bowel-preparation agents sodium picosulphate, sodium phosphate and polyethylene glycol used for colonoscopy have been compared in a questionnaire following a prospective randomized single-blind trial (292 men, 342 women). Regardless of the bowel preparation agent used, women had worse tolerability scores than men, with significance for taste, thirst, nausea, vomiting, bloating, headache, dizziness and sleep disturbance. Men were more likely than women to be willing to take the same bowel preparation again (89% vs 76%) [1].

Reproductive health issues

Regarding teratogenic aspects, please consult Janusmed Drugs and Birth Defects (in Swedish, Janusmed fosterpåverkan).

Other information

In a large British registry study (82450 men, 153264 women), the prevalence of constipation was almost twice as high among women up to the age of 75 years, but higher in men than women among patients aged over 75 years. There was no difference between men and women in choice of laxative (macrogol, lactulose, senna or other laxatives including ispaghula).  The most commonly prescribed laxative in pregnant patients with constipation were lactulose followed by macrogol [2].

Updated: 2020-08-28

Date of litterature search: 2015-08-26


  1. Lawrance IC, Willert RP, Murray K. A validated bowel-preparation tolerability questionnaire and assessment of three commonly used bowel-cleansing agents. Dig Dis Sci. 2013;58:926-35. PubMed
  2. Shafe AC, Lee S, Dalrymple JS, Whorwell PJ. The LUCK study: Laxative Usage in patients with GP-diagnosed Constipation in the UK, within the general population and in pregnancy An epidemiological study using the General Practice Research Database (GPRD). Therap Adv Gastroenterol. 2011;4:343-63. PubMed
  3. Pelham RW, Nix LC, Chavira RE, Cleveland MV, Stetson P. Clinical trial: single- and multiple-dose pharmacokinetics of polyethylene glycol (PEG-3350) in healthy young and elderly subjects. Aliment Pharmacol Ther. 2008;28:256-65. PubMed
  4. Mathus-Vliegen EM, Kemble UM. A prospective randomized blinded comparison of sodium phosphate and polyethylene glycol-electrolyte solution for safe bowel cleansing. Aliment Pharmacol Ther. 2006;23:543-52. PubMed
  5. Di Palma JA, Rodriguez R, McGowan J, Cleveland Mv. A randomized clinical study evaluating the safety and efficacy of a new, reduced-volume, oral sulfate colon-cleansing preparation for colonoscopy. Am J Gastroenterol. 2009;104:2275-84. PubMed
  6. Szojda MM, Kuik DJ, Mulder CJ, Felt-Bersma RJ. Colonic lavage with two polyethylene glycol solutions prior to colonoscopy makes no difference: a prospective randomized controlled trial. Scand J Gastroenterol. 2008;43:622-6. PubMed
  7. Läkemedelsstatistik. Stockholm: Socialstyrelsen. 2015 [cited 2016-04-05.] länk

Authors: Linnéa Karlsson Lind, Desirée Loikas

Reviewed by: Mia von Euler

Approved by: Karin Schenck-Gustafsson