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    Last updated: January 2024


    Therapeutic action

    • Osmotic laxative


    • Prevention of constipation in patients taking opioid analgesics (e.g. codeine, morphine)

    Forms and strengths

    • 10 g/15 ml oral solution, to be administered using a measuring device (oral syringe, measuring spoon, or cup with graduations)

    Dosage and duration

    • Child under 1 year: 5 ml daily (3.3 g daily)
    • Child from 1 to 6 years: 5 to 10 ml daily (3.3 to 6.7 g daily)
    • Child from 7 to 14 years: 10 to 15 ml daily (6.7 to 10 g daily)
    • Child over 14 years and adult: 15 to 45 ml daily (10 to 30 g daily)


    Start lactulose when analgesic treatment continues more than 48 hours.
    Lactulose must be taken daily, until the end of the opioid treatment. Regular follow up (frequency/consistency of stools) is essential in order to adjust dosage correctly.

    Contra-indications, adverse effects, precautions

    • Do not administer to patients with Crohn’s disease, ulcerative colitis, intestinal obstruction, undiagnosed abdominal pain.
    • May cause: abdominal discomfort, flatulence and diarrhoea.
    • In the event of diarrhoea, exclude a faecal impaction and intestinal obstruction; reduce the dose.
    • Pregnancy: no contra-indication
    • Breast-feeding: no contra-indication


    • It may take up to 48 hours, or even longer, before the treatment is effective. Lactulose is not indicated in acute constipation where a rapid result is needed.
    • If necessary, lactulose may be given in combination with a stimulant laxative (e.g. bisacodyl, senna).
    • The oral solution may be taken undiluted, or diluted in water.
    • The treatment should be accompanied by dietary measures (fluids and fibre).


    Below 25 °C. Do not store in a refrigerator (cristallisation).