title: Effects of lactulose and polyethylene glycol on colonic transit.
abstract: BACKGROUND
  The effects of lactulose and polyethylene glycol on colonic transit are poorly established.
  
  
  OBJECTIVE
  To assess the effects of these laxatives on colonic transit in normal subjects.
  
  
  METHODS
  Colonic transit (mean residence time, cumulative counts in stool, counts remaining in the proximal or distal colon) was measured scintigraphically in normal subjects on the second and third day of a 3-day ingestion of 67-134 g/day lactulose, or 59 g/day polyethylene glycol.
  
  
  RESULTS
  At similar stool weight (lactulose: 653 +/- 120 g/day; polyethylene glycol: 522 +/- 66 g/day), transit was significantly slower during 99 g/day lactulose when compared with 59 g/day polyethylene glycol; this was most pronounced in the distal colon (mean residence time: lactulose - 403 +/- 55 min; polyethylene glycol - 160 +/- 41.9 min). Short chain fatty acid concentration in 24-h stool correlated significantly with counts remaining in the distal colon at 12 h (r = 0.79, P = 0.001). Increasing lactulose doses were significantly associated with increasing stool weight (r = 0.79) and shorter mean residence time in the total (r = -0.56) and distal colon (r = -0.64). The sum of faecal carbohydrates plus short chain fatty acids was associated with stool weight (r = 0.95, P < 0.001).
  
  
  CONCLUSIONS
  Lactulose accelerates colonic transit. However, compared with polyethylene glycol, transit during lactulose is prolonged.
authors.affiliation: Universitätsklinik für Innere Medizin IV, Vienna.
authors.forename: E
authors.initials: E
authors.lastname: Fritz
authors.forename: H F
authors.initials: HF
authors.lastname: Hammer
authors.forename: R W
authors.initials: RW
authors.lastname: Lipp
authors.forename: C
authors.initials: C
authors.lastname: Högenauer
authors.forename: R
authors.initials: R
authors.lastname: Stauber
authors.forename: J
authors.initials: J
authors.lastname: Hammer
mesh_terms: D000328:Adult; D002241:Carbohydrates / Q000032:analysis; D002400:Cathartics / Q000494:pharmacology*; D003106:Colon / Q000000981:diagnostic imaging / Q000187:drug effects / Q000382:microbiology*; D003248:Constipation / Q000188:drug therapy / Q000503:physiopathology; D005232:Fatty Acids, Volatile / Q000032:analysis; D005243:Feces / Q000737:chemistry; D005260:Female; D005772:Gastrointestinal Transit / Q000187:drug effects*; D006801:Humans; D007205:Indium Radioisotopes; D007792:Lactulose / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D011092:Polyethylene Glycols / Q000494:pharmacology*; D011877:Radionuclide Imaging; D018709:Statistics, Nonparametric; D013268:Stimulation, Chemical
chemical_list: D002241:Carbohydrates; D002400:Cathartics; D005232:Fatty Acids, Volatile; D007205:Indium Radioisotopes; D011092:Polyethylene Glycols; D007792:Lactulose