Osmotic Laxative — Bowel Preparation / Constipation Pregnancy: Considered safe in pregnancy for constipation; avoid large-volume bowel prep unless clearly indicated

Macrogol (Polyethylene Glycol)

Brand names: Klean-Prep, Moviprep, Laxido

Adult dose

Dose: Bowel prep: 2-4 litres over 4-6 hours (Klean-Prep/Moviprep). Constipation: 1-3 sachets daily (Laxido)

Route: Oral

Frequency: Bowel prep: single course day before procedure; constipation: once to three times daily

Max: 4 litres for bowel preparation

Moviprep (split-dose 1 L + 1 L): half evening before, half morning of procedure — superior colonoscopy quality. Klean-Prep: 4 litres day before. Laxido: 1-3 sachets dissolved in 125 mL water each

Paediatric dose

Dose: 1-1.5 g/kg/day (faecal impaction: up to 4 days); 0.4 g/kg/day (maintenance) g/day/kg

Route: Oral

Frequency: Once daily (maintenance); divided doses (disimpaction)

Max: 8 sachets/day (disimpaction); 4 sachets/day (maintenance)

NICE NG90: macrogol first-line for childhood constipation and faecal impaction. Child 2-11 years: 2-4 sachets/day (disimpaction); 1-4 sachets/day (maintenance)

Dose adjustments

Renal

Use with caution in moderate-severe renal impairment — electrolyte disturbances

Hepatic

No specific adjustment

Paediatric weight-based calculator

Patient weight (kg)

NICE NG90: macrogol first-line for childhood constipation and faecal impaction. Child 2-11 years: 2-4 sachets/day (disimpaction); 1-4 sachets/day (maintenance)

Clinical pearls

Macrogol is an inert polymer that retains water in the bowel by osmosis without being absorbed or metabolised — electrolyte-balanced formulations (Klean-Prep, Moviprep) include sodium, potassium, and bicarbonate to minimise disturbances
Moviprep split-dose: recommended by BSG — better bowel cleanliness scores than day-before full preparation; important for morning colonoscopy procedures
Post-operative ileus: macrogol plus early mobilisation and oral intake are cornerstones of management — avoid stimulant laxatives until bowel sounds return
Paediatric faecal impaction (NICE NG90): macrogol escalating dose disimpaction preferred over manual evacuation — start 2 sachets/day and increase by 2 sachets every 2 days to max 8
Aspiration risk during large-volume prep: position patient upright; contraindicated if unable to swallow safely

Contraindications

Intestinal obstruction or perforation
Ileus
Toxic megacolon
Severe inflammatory bowel disease

Side effects

Nausea, bloating, abdominal cramps (large volume prep)
Electrolyte disturbances (hyponatraemia — particularly with large volumes)
Allergic reactions (rare — to additives in formulation)
Pulmonary aspiration (if vomiting during prep)

Interactions

Drugs with narrow therapeutic window (absorption reduced by rapid GI transit during preparation)

Monitoring

Electrolytes (bowel prep — hyponatraemia risk in elderly)
Fluid balance
Bowel output (prep adequacy)

Reference: BNFc; BNF 90; Moviprep SPC; BSG Bowel Preparation Guidelines; NICE NG90 (Childhood Constipation). Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways