Laxative
Pregnancy: Safe throughout pregnancy — not systemically absorbed; preferred osmotic laxative
Lactulose
Brand names: Duphalac, Lactugal
Adult dose
Dose: 15–30 mL (10–20 g)
Route: Oral
Frequency: Twice daily, adjusted to response
Max: 60 mL/day
First-line osmotic laxative in pregnancy. May take 48 hours for onset. Advised alongside increased fluid and dietary fibre. Also used in hepatic encephalopathy at higher doses.
Paediatric dose
Dose: Age-based dosing mL/kg
Route: Oral
Frequency: Twice daily
Max: 30 mL twice daily in older children
BNFc: neonates 2.5 mL twice daily; 1 month–5 years 2.5–10 mL twice daily; 5–18 years 15 mL twice daily. Adjust dose to produce soft formed stools.
Dose adjustments
Renal
No dose adjustment required
Hepatic
Dose increase used in hepatic encephalopathy (30–50 mL three times daily)
Paediatric weight-based calculator
BNFc: neonates 2.5 mL twice daily; 1 month–5 years 2.5–10 mL twice daily; 5–18 years 15 mL twice daily. Adjust dose to produce soft formed stools.
Clinical pearls
- Preferred osmotic laxative in all trimesters — not absorbed systemically; no fetal risk
- Constipation affects up to 40% of pregnant women — lactulose is the first-line pharmacological option
- Counsel on delayed onset (24–48 hours) and need for adequate fluid intake
- Ispaghula husk (Fybogel) preferred if bulk-forming laxative preferred over osmotic
- Avoid stimulant laxatives (e.g. senna) as second-line only; lactulose first
Contraindications
- Galactosaemia
- Intestinal obstruction
- Lactose intolerance (contains lactose)
Side effects
- Bloating
- Flatulence
- Abdominal cramps
- Nausea
Interactions
- Antacids — may reduce efficacy
Monitoring
- Symptom response
- Fluid balance (if high dose)
Reference: BNFc; BNF 90; BNFc; RCOG (2022) Obstetric pharmacology; NICE CG190. Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.
Calculators
Drugs