Osmotic Laxative
Pregnancy: Safe — macrogol is not absorbed systemically; no teratogenic risk; first-line laxative in pregnancy alongside dietary modification and fibre supplementation
Macrogol (Polyethylene Glycol)
Brand names: Movicol, Laxido, CosmoCol
Adult dose
Dose: Constipation: 1–3 sachets/day (each sachet dissolved in 125 mL water); Faecal impaction: 8 sachets within 6 hours daily for up to 3 days
Route: Oral (dissolved in water)
Frequency: Once to three times daily
Max: 8 sachets/day for impaction (3-day course maximum)
Each Movicol sachet contains macrogol 3350 13.125 g + electrolytes; must be dissolved in at least 125 mL water; impaction regimen should not be used if bowel obstruction suspected; excess fluid intake important
Paediatric dose
Dose: Paediatric Movicol: 1–4 sachets/day for constipation; impaction: higher doses per weight (see BNFc) sachets/day/kg
Route: Oral
Frequency: Once to four times daily
Max: Age-dependent (BNFc)
Paediatric Movicol (half-strength) licensed ≥2 years; first-line for childhood constipation (NICE CG99); disimpaction regimen per BNFc weight-based guidance
Dose adjustments
Renal
Caution with impaction regimen in renal impairment — electrolyte formulation; standard constipation doses safe
Hepatic
No dose adjustment required
Paediatric weight-based calculator
Paediatric Movicol (half-strength) licensed ≥2 years; first-line for childhood constipation (NICE CG99); disimpaction regimen per BNFc weight-based guidance
Clinical pearls
- NICE CG99 (Constipation in Children): macrogol-based laxatives are first-line for both disimpaction and maintenance treatment of childhood constipation — superior to lactulose in evidence; adequate fluid intake alongside macrogol is essential for effectiveness
- Mechanism: macrogol (polyethylene glycol) is an osmotically active polymer — retains water in the bowel lumen by hydrogen bonding; increases stool volume and softens consistency; unlike stimulant laxatives (senna, bisacodyl), causes no electrolyte loss or cramping at standard doses
- Electrolyte-containing formulation advantage: Movicol contains sodium bicarbonate, sodium chloride, and potassium chloride — prevents electrolyte disturbance during impaction regimen; pure macrogol preparations (without electrolytes) may cause hyponatraemia at high doses
- Opioid-induced constipation: macrogol is commonly used — however, opioid-induced constipation is driven by mu-receptor activation in gut (not just stool hardness), so peripherally-acting mu-opioid antagonists (naloxegol, methylnaltrexone) are more targeted and effective for refractory cases
- Patient adherence: unpleasant taste is the main compliance barrier — dissolving in fruit juice (apple/orange) is acceptable; chilling the solution can improve palatability; flavoured versions available (Laxido Orange)
Contraindications
- Suspected intestinal obstruction
- Intestinal perforation
- Toxic megacolon
- Ileus
Side effects
- Bloating and flatulence (most common)
- Abdominal cramps
- Nausea
- Diarrhoea (if too high a dose)
- Electrolyte disturbances (impaction doses — rare at standard doses)
Interactions
- No significant drug interactions — not absorbed systemically
Monitoring
- Bowel habit diary (frequency, consistency — Bristol stool chart)
- Abdominal examination (impaction palpation)
- Electrolytes (with impaction regimen)
- Adequate fluid intake (record)
Reference: BNFc; BNF 90; BNFc; NICE CG99 (Constipation in Children 2010); NICE CKS Constipation; SPC Movicol; Cochrane Review — laxatives for chronic constipation. Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.
Calculators