Makindo Medical Notes

⚡ Bisacodyl is a stimulant laxative that increases intestinal motility and fluid secretion. When taken orally, it acts within 6–12 hours; rectal suppositories act more rapidly (within 15–60 minutes). Best used short-term for acute constipation or bowel preparation.

🧠 About

• A diphenylmethane derivative that directly stimulates the colonic mucosa.
• Hydrolysed in the intestine to the active metabolite bis-(p-hydroxyphenyl)-pyridyl-2-methane (BHPM).
• Available as oral tablets and rectal suppositories.
• Commonly used in hospital bowel-prep regimens before procedures (e.g. colonoscopy, barium enema, surgery).

⚙️ Mode of Action

• Acts directly on the enteric nervous system of the colon to increase peristalsis.
• Stimulates mucosal chloride and water secretion, softening stool and accelerating transit.
• Minimal effect on small intestine — action is almost entirely colonic.
• Oral form is activated in the distal colon after deacetylation by intestinal enzymes.

🎯 Indications

• Short-term treatment of constipation.
• Bowel preparation prior to radiological or surgical procedures.
• Adjunctive therapy for opioid-induced constipation (with stool softeners or osmotic agents).

💊 Dose

• Constipation: 5–10 mg orally at night or in the morning. Onset 6–12 h.
• Suppository: 10 mg PR for rapid effect (15–60 min).
• Bowel prep: 10 mg twice daily for up to 3 doses in the 24 h preceding the procedure (check local protocol).

📋 Typical Adult Dose Range

⚠️ Cautions

• Encourage hydration and mobility to reduce cramping and dehydration.
• Use short-term only (≤5 days) to avoid dependence or colonic atony.
• Stop if abdominal pain, nausea, or vomiting suggest obstruction.
• Chronic use can cause hypokalaemia and metabolic alkalosis from fluid loss.

🚫 Contraindications

• Intestinal obstruction or ileus.
• Acute inflammatory bowel disease (e.g. Crohn’s, ulcerative colitis).
• Severe dehydration or electrolyte imbalance.
• Undiagnosed acute abdominal pain (rule out surgical causes).

💊 Adverse Effects

• Common: Abdominal cramps, diarrhoea, nausea.
• Occasional: Colitis, rectal irritation (if suppository used), electrolyte imbalance.
• Rare: Faintness or vasovagal episodes following rectal use.

🤰 Pregnancy & Lactation

• Generally considered safe for short-term use during pregnancy — minimal systemic absorption.
• Can be used in breastfeeding; metabolites not found in breast milk.

🩺 Clinical Pearls

• Best given at night for next-morning effect (oral form).
• Combine with an osmotic laxative (e.g. macrogol) for opioid-induced constipation.
• Prefer suppository if oral intake is restricted or urgent relief is needed.
• Chronic use may cause a ‘lazy bowel’ — avoid daily long-term administration.

💡 Teaching Tip

• Compare stimulant mechanisms: Senna → plant-derived anthraquinone stimulating mucosa Bisacodyl → synthetic compound acting directly on mucosal nerve endings.
• Highlight that bisacodyl suppositories are one of the fastest acting forms of stimulant laxatives — useful for acute faecal loading.

📚 References

• BNF: Bisacodyl
• NICE CKS: Constipation in adults (2024)
• Camilleri M. NEJM 2021;385:488–498 — Mechanisms and management of chronic constipation.