Bulk-forming agents

Bulk-forming laxative agents include:

• bran
• ispaghula husk
• methylcellulose
• sterculia granules

Bulk-forming laxatives:

• have been shown to decrease abdominal pain and improve stool consistency
• are only required if dietary fibre cannot be increased sufficiently - an effective bulk-forming preparation is unprocessed wheat bran (taken with food or fruit juice)
• are not appropriate for acute relief, as they may take several days to work, but they are a good option for long-term control
• increase stool bulk, with the increased stool bulk then stimulating peristalsis; clearly, to prevent obstruction, fluid intake must be maintained

It is essential to drink adequate amounts of fluid when using bulk-forming laxatives to avoid intestinal obstruction. Flatulence and abdominal distension are the most common side effects.

Bulk-forming laxatives are contraindicated in patients with existing bowel obstruction or faecal impaction, and they are not recommended in opioid-induced constipation.

References:

1. Krogh K, Chiarioni G, Whitehead W; Management of chronic constipation in adults. United European Gastroenterol J. 2017 Jun;5(4):465-472.
2. NICE. Constipation in children and young people: diagnosis and management. Clinical guideline CG99. Published May 2010, last updated July 2017.