Laxatives

Note for Physician Associates (PAs):
PAs cannot currently prescribe laxatives independently. Always consult your supervising clinician. This ladder supports clinical reasoning and safe escalation.
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1. Bulk-forming laxatives

Examples: Ispaghula husk (Fybogel)

Mechanism: increases stool bulk by absorbing water - stimulates peristalsis

Use: first-line for chronic constipation; suitable for long-term use

Notes: ensure adequate fluid intake to prevent obstruction. Not suitable in opioid-induced constipation.

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2. Osmotic laxatives

Examples: Lactulose, Macrogol (Movicol, Laxido)

Mechanism: draws water into the bowel to soften stools

Use: second line or adjunct to bulk formers

Notes: often causes bloating initially. Macrogol preferred for faecal impaction. Lactulose can take 2-3 days to work.

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3. Stimulant laxatives

Examples: Senna, Bisacodyl

Mechanism: stimulates colonic nerves to increase peristalsis

Use: short term relief or for opioid induced constipation

Notes: Onset within 6-12 hours. Avoid long term use due to risk of bowel dependency.

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4. Stool softeners / Lubricants

Examples: Docusate

Mechanism: softens stools by reducing surface tension

Use: adjunct for hard stools or painful defecation

Notes: often used with other agents. Not for long term use alone. Monitor for electrolyte imbalance.

Escalation Advice:
Red flags such as weight loss, rectal bleeding, change in bowel habit, or iron deficiency anaemia should prompt urgent investigation. Consider 2WW referral if appropriate.
References:
- NICE CKS. Constipation in adults. Last revised May 2023.
- BNF. Laxatives. Available at: bnf.nice.org.uk
- South East London ICS Formulary. Bowel management in primary care.

NICE Laxative Ladder

  • Fibre: 20-30g/day + 1.5–2L/day fluid intake
  • Example: Ispaghula husk (Fybogel): 1 sachet BD
  • Mechanism: increases stool bulk to stimulate peristalsis
  • Note: Avoid in opioid-induced constipation
  • First-line: Macrogol (Movicol / Laxido): 1-2 sachets OD–BD
  • Alternative: Lactulose 15 ml BD
  • Mechanism: draws water into the colon to soften stool
  • Note: bloating common initially. Ensure adequate hydration.
  • Examples:
    • Senna: 7.5-15 mg at night
    • Bisacodyl: 5-10 mg at night (oral) or 10 mg PR
  • Mechanism: stimulates enteric nerves to increase motility
  • Use: short term or opioid induced constipation
  • Day 1: 8 sachets of Macrogol over 6-12 hours (1 sachet every 1.5 hrs) each dissolved in 125ml water, total 1L
  • Day 2: repeat 8 sachets if no bowel movement
  • Day 3: repeat 8 sachets. If still impacted, add:
    • Senna 15 mg at night
    • OR Bisacodyl 10 mg PR

Maintenance: 1-2 sachets/day once disimpacted

Alternative if not tolerated: lactulose 15 ml BD + Bisacodyl 10 mg PR

Enema: glycerin or phosphate enema under GP/senior guidance if oral therapy fails

  • Macrogol (Movicol Paediatric Plain): use escalating daily doses
  • 2-6 years: start with 2 sachets on day 1, increase by 2 daily (max 8)
  • 7-11 years: start with 4 sachets on day 1, increase by 2 daily (max 12)
  • Mix each sachet in 62.5 ml water
  • Once disimpacted → reduce to maintenance (1 sachet/day)

Stimulants (if needed): add Senna or Bisacodyl if macrogol alone insufficient

Note: always review for safeguarding, withholding behaviour or underlying conditions

  • No bowel sounds or severe abdominal pain
  • Vomiting or abdominal distension
  • Signs of dehydration or confusion (especially elderly)
  • Rectal bleeding, weight loss, or anaemia

Referral: consider urgent or 2WW if cancer is suspected

References:
- NICE CKS. Constipation in adults. May 2023
- NICE NG158. Constipation in children. July 2022
- BNF / BNFc. Laxatives & Macrogol
- SEL ICS Formulary. Constipation & Faecal Impaction Guidelines