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Laxative Pregnancy: A — safe throughout pregnancy

Lactulose

Brand names: Lactulose Solution

Adult dose

Dose: Constipation: 15ml BD. Hepatic encephalopathy: 30–50ml TDS (titrate to 2–3 soft stools/day)
Route: Oral
Frequency: Twice daily (constipation); 3–4 times daily (HE)
Max: Hepatic encephalopathy: 200ml/day
Onset 24–48h. Mix with water or juice. Hepatic encephalopathy: aim for 2–3 loose stools per day — acidifies colon, reduces NH₃ absorption.

Paediatric dose

Dose: 0.5 mL/kg
Route: Oral
Frequency: Twice daily
Max: 15ml
Age bands
  • 0–12m: 2.5ml BD
  • 12–60m: 5ml BD
  • 60–144m: 10ml BD
Paediatric weight-based calculator

Clinical pearls

  • Hepatic encephalopathy: lactulose acidifies the colon — NH₃ converted to NH₄⁺ which is not absorbed. First-line treatment (NICE NG215).
  • Target 2–3 soft stools per day in HE — reduce dose if diarrhoea.
  • SONIC trial: rifaximin + lactulose superior to lactulose alone for secondary prevention of overt HE.
  • Not absorbed — osmotic agent. Onset 24–48h (slower than stimulant laxatives).

Contraindications

  • Galactosaemia
  • Intestinal obstruction
  • Severe inflammatory bowel disease

Side effects

  • Flatulence and bloating (very common — especially initially)
  • Abdominal cramps
  • Diarrhoea (if overused)
  • Nausea

Interactions

  • Antacids: may reduce lactulose efficacy (neutralise colonic acidification)

Monitoring

  • Stool frequency
  • electrolytes if high doses (diarrhoea)
  • ammonia level (HE)

Reference: BNFc; NICE NG215 Cirrhosis; NICE BNF 84. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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