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  • lactulose is a sugar which is not absorbable from the gut and hence is used as a laxative for the treatment of constipation and hepatic encephalopathy (can be given rectally for ammonia reduction)
  • it is made from heating lactose
  • it is marketed as Duphalac or Actilax (3.3g lactulose per 5mL)
  • can be used in pregnancy


  • onset is 1-2 days
  • osmotic effects of lactulose itself and some of its metabolites
    • increases bowel osmotic pressure and thus increases water content in stool which allows the stool to be softer but in higher amounts may cause diarrhoea
  • peristaltic effect of some of the metabolites (eg. acetate)
  • ammonia-trapping effect
    • metabolites include lactic acid and acetic acid which acidify the stool and can thus convert ammonia into ammonium which is then excreted with stool which helps in patients with hepatic encephalopathy

Adverse effects

  • fermentation in colon produces gas production (eg. methane) which causes:
    • increased flatulence, borborygmi, abdominal cramps, nausea
  • excessive osmotic amount will cause diarrhoea

Oral dosing

  • should also drink plenty of fluids and ensure adequate dietary fibre intake
  • adults
    • 15-30mL daily
    • after 3 days may reduce dose to 10-25mL daily
  • children
    • under 1yr: 5mL/day reducing to 3-5mL/day
    • 1-6yrs: 10mL/day reducing to 5-10mL/day
    • 7-14rs: 15mL/day reducing to 10mL/day
lactulose.txt · Last modified: 2019/06/27 03:29 by

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