Bisacodyl — NZ Medication Guide
📋 Reviewed by a Registered Pharmacist NZ — This information is for general educational purposes only and does not replace professional medical advice. Always consult your doctor or pharmacist before starting, stopping, or changing any medication.
What is Bisacodyl?
Bisacodyl is a stimulant laxative used for the short-term treatment of constipation and for bowel preparation before medical procedures. This medication is available over-the-counter; also funded by Pharmac.
What is Bisacodyl Used For?
Bisacodyl is used for short-term treatment of constipation, and as part of bowel preparation before colonoscopy, surgery, or imaging procedures. Available as oral tablets and rectal suppositories.
How Does Bisacodyl Work?
Bisacodyl is a prodrug hydrolysed by intestinal enzymes to the active form (bis-(p-hydroxyphenyl)-pyridyl-2-methane). It acts on the large intestinal mucosa to stimulate sensory nerve endings — increasing gut motility and promoting secretion of water and electrolytes into the colon — producing a bowel action within 6–12 hours (oral) or 15–30 minutes (rectal).
How to Take Bisacodyl
Oral tablet (5–10 mg): taken at bedtime for a bowel action next morning. Swallow whole with water — do not crush, chew, or take within 1 hour of antacids or milk (which dissolve the enteric coating prematurely). Rectal suppository (10 mg): inserted rectally, produces action in 15–30 minutes. Do not use for more than 2–3 consecutive days.
Common Side Effects of Bisacodyl
- Abdominal cramping (expected)
- Nausea
- Diarrhoea (with excessive doses)
Serious Side Effects — Seek Medical Attention
Contact your doctor or call 111 immediately if you experience any of the following:
- Electrolyte imbalance (with prolonged overuse — hypokalaemia)
- Chronic laxative dependency (with prolonged daily use)
- Melanosis coli (brown discolouration of colon mucosa — benign, with long-term stimulant laxative use)
Drug Interactions
Bisacodyl may interact with other medicines. Always inform your doctor and pharmacist of all medications you are taking. Key interactions include:
- Antacids and milk (dissolve enteric coating — take 1 hour apart)
- Diuretics (additive hypokalaemia risk with excessive laxative use)
New Zealand Prescribing Information
Bisacodyl (5 mg enteric-coated tablets; 10 mg suppositories — Dulcolax® and generics) is available OTC at NZ pharmacies. Short courses are appropriate for constipation. Long-term use should prompt investigation of the underlying cause of constipation. For constipation in patients on opioid therapy or with chronic constipation, an osmotic laxative (lactulose, macrogol) and a stimulant laxative (senna or bisacodyl) in combination may be needed.
Frequently Asked Questions
Why can’t I take bisacodyl with milk or antacids?
Bisacodyl tablets have an enteric coating that prevents them from dissolving in the stomach (to avoid stomach irritation). Antacids, milk, or dairy products neutralise gastric acid and dissolve this coating prematurely, causing stomach irritation and cramping. Take bisacodyl at least 1 hour after any such products.
Can I use bisacodyl long-term?
No — bisacodyl is intended for short-term use only (2–3 days maximum without medical advice). Long-term daily use can cause dependence, chronic diarrhoea, electrolyte imbalance, and eventually a sluggish bowel. If you need daily laxatives, consult your GP for assessment of the underlying cause.
⚠️ Disclaimer: This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified health provider. In New Zealand, medication availability and funding may vary — check with Pharmac or your pharmacist for current information.
Reviewed by a Registered Pharmacist NZ
References & Further Information
The following New Zealand and international resources were used to inform this page: