Osmotic Laxative — Constipation / Hepatic Encephalopathy Pregnancy: 'No effects during pregnancy are anticipated, since systemic exposure to lactulose is negligible. Duphalac can be used during pregnancy.' Breast-feeding: 'No effects on the breastfed newborn/infant are anticipated since the systemic exposure of the breast-feeding woman to lactulose is negligible. Duphalac can be used during breast-feeding.' Fertility: no effects are to be expected (§4.6).

Lactulose (Paediatric)

Brand names: Duphalac, Lactugal

Paediatric lactulose, an osmotic laxative, used in children for constipation and, at higher doses, in the management of hepatic encephalopathy.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Constipation (adults and adolescents): starting dose 15–45 ml daily (1–3 sachets), maintenance dose 15–30 ml daily (1–2 sachets). Hepatic encephalopathy (adults): starting dose 30–45 ml (6–9 x 5 ml spoonfuls, or 2–3 sachets) three to four times daily

Route: Oral — the solution may be administered diluted or undiluted; each dose may be taken with water or fruit juices and should be swallowed in one and not kept in the mouth for an extended period

Frequency: Constipation: as a single daily dose (taken at the same time each day, e.g. during breakfast) or in two divided doses. Hepatic encephalopathy: 3 to 4 times daily, adjusted to the maintenance dose to achieve two or three soft stools each day

SOURCE: eMC UK SPC, productName 'Duphalac 3.335 g/5 ml Oral Solution', §4.2 (bottles or 15 ml single-dose sachets; 15 ml = 1 sachet). 'The posology should be adjusted according to the individual needs of the patient.' After a few days the starting dose may be adjusted to the maintenance dose based on treatment response; several days (2–3 days) of treatment may be needed before an effect occurs. Recommend drinking sufficient fluid (1.5–2 litres, equal to 6–8 glasses) during the day while on laxative therapy. PAEDIATRIC CONSTIPATION doses are VOLUME-based, not per-kg, which is why paedDose is null — VERBATIM §4.2 table (starting dose daily / maintenance dose daily): children 7–14 years — 15 ml (1 sachet) / 10–15 ml (1 sachet, and 'If the maintenance dose is below 15 ml, lactulose in bottles should be used'); children 1–6 years — 5–10 ml / 5–10 ml; infants under 1 year — up to 5 ml / up to 5 ml. 'For a precise dosing for infants and children up to 7 years lactulose in bottles should be used.' PAEDIATRIC HEPATIC ENCEPHALOPATHY: 'The safety and efficacy in children (newborn to 18 years of age) with HE have not been established. No data are available' — this SPC gives NO paediatric HE dose. 'Use of laxatives in children should be exceptional and under medical supervision' (§4.4). EXCIPIENT WARNING: the product contains lactose, galactose and fructose from the route of production — patients with rare hereditary problems of galactose or fructose intolerance, total lactase deficiency or glucose-galactose malabsorption should not take this medicine; it also contains sulphite, and should be given with care to patients intolerant to lactose. Verify all under-18 dosing against a children's formulary.

Dose adjustments

Renal

'Elderly patients and patients with renal or hepatic insufficiency: No special dosage recommendations exist, since systemic exposure to lactulose is negligible' (§4.2).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients
Galactosaemia
Gastro-intestinal obstruction, perforation or risk of perforation

Side effects

Diarrhoea (very common)
Flatulence, abdominal pain, nausea and vomiting (common) — flatulence may occur during the first few days of treatment and as a rule disappears after a couple of days
Abdominal pain and diarrhoea when dosages higher than instructed are used — the dosage should then be decreased
Electrolyte imbalance due to diarrhoea (uncommon), particularly if high doses (normally only associated with hepatic encephalopathy) are used for an extended period — adjust the dosage to obtain two or three formed stools per day
Hypersensitivity reactions (not known); rash, pruritus and urticaria (post-marketing experience)

Interactions

'No interaction studies have been performed' (SPC §4.5)
Neomycin and possibly other oral anti-infective agents — theoretically, elimination of certain colonic bacteria may interfere with the desired degradation of lactulose and prevent acidification of colonic contents; monitor the lactulose-treated patient closely during concomitant oral anti-infective therapy (US label)
Non-absorbable antacids given concurrently — preliminary studies suggest they may inhibit the desired lactulose-induced drop in colonic pH (US label)
Other laxatives — should not be used, especially during the initial phase of therapy for portal-systemic encephalopathy, because the resulting loose stools may falsely suggest that adequate lactulose dosage has been achieved (US label)

Clinical monograph

How it works

A non-absorbed disaccharide that draws water into the bowel by osmosis to soften stool and promote peristalsis; colonic bacterial fermentation also acidifies the lumen, reducing ammonia absorption in hepatic encephalopathy.

Prescribing in practice

Maintain adequate fluid intake during treatment, as lactulose works osmotically and the dose is titrated to produce soft, regular stools.
Its effect is not immediate and may take a couple of days, so it is for regular rather than rapid relief.
Use caution in lactose intolerance or galactosaemia and confirm paediatric dosing against a children's formulary.

Monitoring

Monitor stool frequency and consistency and the child's hydration, titrating the dose to response.

Counselling the patient

Encourage plenty of fluids while taking lactulose.
Explain it may take a day or two to work and the dose is adjusted to keep stools soft.
Flatulence or cramps may occur initially and usually settle.

Evidence & guidelines

Lactulose is an established osmotic laxative for childhood constipation, used alongside other measures per NICE constipation guidance.

Reference: NICE NG90 (Constipation in Children); ESPGHAN Childhood Constipation Guidelines 2014; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways