Bisacodyl !
A stimulant laxative that makes the bowel contract. Tablets act overnight, suppositories much faster; also used to empty the bowel before procedures.
Updated 2026-11-01
Mechanism of action
Bisacodyl, a diphenylmethane derivative, is converted in the gut to its active deacetylated form. This stimulates the enteric nerves of the colon and increases the secretion of water and electrolytes into the lumen, so contractions and stool water both rise. Tablets have an enteric coating so the drug is released in the bowel, not the stomach.
- Enteric-coated tablet passes the stomach intact
- Converted in the gut to its active deacetylated form
- Stimulates colonic nerves and fluid secretion
- Stronger contractions produce a bowel movement
Pharmacokinetics
- Absorption
- Minimal systemic absorption
- Metabolism
- Converted in the gut to the active deacetylated metabolite
- Onset and duration
- Tablets usually act in 6 to 12 hours; suppositories act much faster
Indications
- Short-term relief of constipation Constipation and faecal impaction →
- Emptying the bowel before surgery, colonoscopy and other procedures
Adverse effects
Common
- Abdominal cramps
- Stomach discomfort
- Faintness
Contraindications
- Inability to swallow the tablet without chewing it
- Abdominal pain, nausea or vomiting of unknown cause, or suspected bowel obstruction
Key interactions
- Antacids and milk
- Taken within an hour of the tablet, they can dissolve the coating early and irritate the stomach
What is monitored
- Bowel movements and abdominal cramps
- Rectal bleeding
- Fluid and electrolytes with repeated use or bowel preparation
Administration and safety
- Tablets are swallowed whole with water and never chewed or crushed.
- Not taken within an hour of antacids or milk.
- Tablets are often given in the evening so the bowel movement comes the next morning.
Nursing care
- Ask about abdominal pain, vomiting or a sudden change in bowel habit before giving it.
- Tell the patient to expect cramps and to report rectal bleeding or no bowel movement.
- Teach that regular long-term use without medical advice is avoided.
- Encourage fibre, fluids and activity as the base of bowel care.
Pregnancy and breastfeeding
Not generally recommended in pregnancy unless diet and lifestyle measures fail; it is not thought to pass into breast milk.
Test yourself
Think of the answer, then tap the question to see it.
Why are bisacodyl tablets not taken with milk or antacids?
They can dissolve the enteric coating in the stomach, causing stomach irritation and cramps.
How does bisacodyl produce a bowel movement?
Its active deacetylated form stimulates the enteric nerves and fluid secretion of the colon.
Besides constipation, what is bisacodyl used for?
To empty the bowel before surgery, colonoscopy and other procedures.
Related drugs
Related conditions
← Back to the class: Laxatives
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - BISACODYL tablet, delayed release (DailyMed (U.S. National Library of Medicine), 2026); Bisacodyl: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2018); Bisacodyl: a laxative taken to treat constipation - NHS (NHS (National Health Service, UK), 2024); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 62 (McGraw Hill, 2025).
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