Bisacodyl 💊
⚡ 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
| Formulation | Dose | Frequency | Route |
|---|
| Bisacodyl tablets | 5–10 mg | Once daily | Oral |
| Bisacodyl suppository | 10 mg | Once daily | Rectal |
| Bowel prep (per protocol) | 10 mg | Twice daily | Oral |
⚠️ 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.
