bisacodyl
stimulant laxative· Brands: Dulcolax, Dulco, BisalaxPOPR
Mechanism of action
Bisacodyl is a diphenylmethane derivative that is hydrolysed in the colon to its active metabolite. This metabolite stimulates colonic mucosal afferent nerves and the myenteric plexus, increasing peristalsis and luminal fluid secretion, resulting in a laxative action.
Pharmacokinetics
Bisacodyl is a prodrug that is activated by hydrolysis in the colon. After oral administration, the enteric coating allows release in the colon, where it is converted to the active metabolite. Onset of action is 6-12 hours after oral administration and 15-60 minutes after rectal use. The active metabolite acts locally, with minimal systemic absorption; small amounts of conjugated drug are excreted in urine and the remainder is excreted in faeces.
Indications & dosing
Constipation
Take at night for effect in the morning. Avoid prolonged use.
- adult · PO: 5–10 mg once daily · Take at night for effect in the morning. Avoid prolonged use.
Constipation
Works within 15-60 minutes. Use as single dose; avoid in anal fissures.
- adult · PR: 10 mg once daily · Works within 15-60 minutes. Use as single dose; avoid in anal fissures.
Contraindications & precautions
- Intestinal obstruction · Bisacodyl is contraindicated in intestinal obstruction; it may increase bowel motility and cause perforation.
- Acute abdominal pain (e.g., appendicitis) · May mask or worsen the underlying condition.
- Severe dehydration · Use with caution; ensure hydration.
- Inflammatory bowel disease · May exacerbate symptoms; avoid in active flare-ups.
- Avoid prolonged use (more than 5 to 7 days) as it may lead to dependence and atonic colon.
- Ensure adequate fluid intake to prevent dehydration and electrolyte imbalance.
- Use with caution in pregnancy and breastfeeding; do not use in children under 10 years without medical advice.
- Monitor electrolyte levels in patients at risk, such as those with renal impairment or taking diuretics.
Adverse effects
- Abdominal cramps
- Diarrhea
- Nausea and vomiting
- Electrolyte imbalanceserious
- Atonic colonserious
- Hypersensitivity reactionsserious
Monitoring, pregnancy & toxicity
- Bowel function · During treatment
- Electrolytes · In prolonged use or with excessive doses
- Pregnancy: Generally considered safe in pregnancy; use only if dietary measures and bulk-forming laxatives are insufficient. Short-term use preferred.
- Toxicity: Diarrhoea · Discontinue; ensure adequate hydration; correct electrolyte imbalance if significant.
- Toxicity: Abdominal cramps · Symptomatic; discontinue if severe. Avoid prolonged use.
Clinical notes
For short-term management of constipation and for bowel preparation before procedures. Oral tablets should be swallowed whole; they must not be crushed or chewed, to avoid premature dissolution in the stomach. Do not take within 1 hour of antacids or milk, as this may erode the enteric coating. The rectal route is useful for acute constipation or as an adjunct for evacuation. Prolonged use may cause electrolyte disturbances and colon laxative dependence. Contraindicated in intestinal obstruction, acute inflammatory bowel disease, and severe dehydration. Caution in pregnancy and children. Advise patients to drink adequate fluids.
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BNF; local formulary