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Bulk-Forming Laxative Pregnancy: Compatible — first-line bulk-forming laxative in pregnancy; not absorbed.

Ispaghula Husk

Brand names: Fybogel, Metamucil, Regulan

Adult dose

Dose: 1 sachet (3.5g) dissolved in 150mL water, taken once to three times daily.
Route: Oral
Frequency: Once to three times daily (after meals)
Max: 3 sachets/day (10.5g/day)
Mix sachet in full glass of water (≥150mL) and drink immediately — do not take dry (risk of oesophageal obstruction). Onset 12–24 hours (bulk-forming). NICE CG61: first-line for IBS with predominant constipation. Also lowers cholesterol (reduces LDL by ~5–7%).

Paediatric dose

Route: Oral
Frequency: Twice daily
Max: 1 sachet per dose
BNF for Children: 6–11 years: ½ sachet (1.75g) twice daily; 12–17 years: 1 sachet twice daily. Must be taken with full glass of water. Source: BNF for Children 2024.

Dose adjustments

Renal

No dose adjustment required.

Hepatic

No dose adjustment required.

Clinical pearls

  • NICE CG61 (IBS): ispaghula husk is first-line dietary supplement for IBS-C (constipation predominant). Advise patient bloating may worsen initially — persevere for 4 weeks.
  • Must be taken with at least 150mL water — risk of oesophageal or intestinal obstruction if taken dry. Never give to bedridden patients who cannot maintain upright position.
  • Cholesterol lowering: soluble fibre reduces LDL by ~5–7% — useful add-on in hypercholesterolaemia.
  • Fybogel sachets are orange-flavoured or unflavoured — check patient preference for adherence.

Contraindications

  • Intestinal obstruction or stricture
  • Difficulty swallowing (risk of oesophageal obstruction if taken dry or without adequate water)
  • Faecal impaction

Side effects

  • Flatulence and bloating (especially in first 1–2 weeks — usually settles)
  • Abdominal distension
  • Oesophageal obstruction (if taken without adequate fluid)
  • Allergic reactions (rare — cross-reactivity with psyllium plant allergy)

Interactions

  • Multiple oral drugs: reduces absorption if taken simultaneously — separate by at least 1 hour
  • Digoxin / warfarin / salicylates: reduced absorption — take at least 1 hour apart

Monitoring

  • Stool consistency and frequency
  • Adequate fluid intake

Reference: BNFc; BNF 90; NICE CG61 Irritable Bowel Syndrome. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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