Makindo Medical Notes

💩 Methylcellulose is a bulk-forming laxative used to relieve constipation by increasing stool bulk and stimulating colonic peristalsis. It is the most physiological class of laxative, acting similarly to dietary fibre — ideal for long-term management where lifestyle modification alone is insufficient.

🧠 About

• Derived from plant cellulose; forms a viscous gel when hydrated.
• Acts locally within the gut — not absorbed systemically.
• Requires adequate fluid intake to avoid impaction.
• Onset of effect: usually within 2–3 days.

⚙️ Mechanism of Action

• Methylcellulose absorbs water in the intestinal lumen, increasing stool mass and water content.
• The increased faecal bulk stretches the bowel wall, triggering mechanoreceptor-mediated peristalsis via the myenteric plexus.
• Softens stool consistency and promotes regular defecation without causing urgency or cramps.

🎯 Indications

• Functional (simple) constipation, especially due to low-fibre diet or immobility.
• Postpartum or post-surgical constipation when straining is undesirable.
• May help in IBS with predominant constipation (IBS-C).
• Sometimes used to firm stools in mild diarrhoea (absorptive effect).

💊 Dose

• Methylcellulose 3–6 tablets twice daily (PO), taken with at least 300 mL of water per dose.
• Alternatively, as granules mixed with a full glass of water or juice.
• Always ensure the patient understands the importance of hydration to prevent obstruction.

⚠️ Cautions

• Maintain good hydration and mobility to optimise efficacy.
• Must be taken with sufficient fluids; otherwise, may form a gelatinous bolus in the oesophagus or intestine.
• Not suitable for bedbound, poorly hydrated, or frail patients — use osmotic laxatives instead.

🚫 Contraindications

• Intestinal obstruction or ileus.
• Stenosing bowel lesions or colonic atony.
• Faecal impaction or severe faecal loading.
• Dysphagia (risk of oesophageal obstruction).
• Infective or inflammatory bowel disease (risk of perforation).

💊 Adverse Effects

• Flatulence, abdominal distension, and mild cramping (due to fermentation by colonic bacteria).
• Rarely: gastrointestinal obstruction or oesophageal blockage if taken without adequate fluid.
• Allergic reactions are extremely rare.

🧩 Comparison with Other Laxatives

📋 Practical Points

• Always combine with lifestyle measures: fibre intake, hydration, and physical activity.
• Warn patients that abdominal bloating may occur initially but usually settles.
• Not habit-forming — safe for long-term use if tolerated.
• If no response after several days, consider adding an osmotic or stimulant laxative.

📚 References

• BNF: Methylcellulose
• NICE CKS: Constipation in Adults (2024)
• Ford AC et al. BMJ 2014;349:g6614. “Efficacy of fibre and laxatives in chronic constipation.”