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Stimulant Laxative — Bowel Preparation / Post-operative Pregnancy: §4.6 verbatim: 'Fertility: No studies on the effect on human fertility have been conducted. Pregnancy: There are no adequate and well-controlled studies in pregnant women. Long experience has shown no evidence of undesirable or damaging effects during pregnancy. Lactation: Clinical data show that neither the active moiety of bisacodyl (BHPM or bis-(p-hydroxyphenyl)-pyridyl-2-methane) nor its glucuronides are excreted into the milk of healthy lactating females. Nevertheless, as with all medicines, bisacodyl should not be taken in pregnancy, especially the first trimester, and during breast feeding unless the expected benefit is thought to outweigh any possible risk and only on medical advice.'

Bisacodyl

Brand names: Dulcolax

Bisacodyl is a stimulant laxative available as oral tablets or suppositories, used for short-term relief of constipation and for bowel evacuation before surgery, endoscopy, or radiological procedures.

Adult dose

Dose: Constipation (including post-operative constipation), adults and children over 12 years: 1 to 2 coated tablets (5 – 10 mg) daily before bedtime. Start with the lowest dose and adjust upwards only as needed. Each coated tablet contains 5 mg — the strength is pinned by the product, 'Bisacodyl 5mg Laxative Tablets 12+ years'. NOT A BOWEL-PREPARATION DOSE, and not a suppository dose: neither is in this source.
Route: Oral — enteric-coated tablets. §4.2 verbatim: 'It is recommended to take the coated tablets at night to have a bowel movement the following morning. They should be swallowed whole with an adequate amount of fluid. The coated tablets should not be taken together with products which reduce the acidity of the upper gastrointestinal tract, such as milk, antacids or proton pump inhibitors, in order not to prematurely dissolve the enteric coating.'
Frequency: Once daily, before bedtime.
Max: Maximum 10 mg (2 coated tablets) daily — the top of the only range stated for this indication. §4.2 verbatim: 'Adults and children over 12 years: 1 to 2 coated tablets (5 - 10 mg) daily before bedtime… It is recommended to start with the lowest dose. The dose may be adjusted up to the maximum recommended dose to produce regular stools. The maximum daily dose should not be exceeded.' No figure above 10 mg daily appears anywhere in the fetched SPC — the '20 mg/day (oral)' ceiling currently shown on this page is not sourced and is double the SPC's.
⚠️ SCOPE — WHAT THIS DOSE IS AND IS NOT. It is the licensed oral constipation posology from the UK SPC for a 5 mg laxative tablet, which is exactly the regimen this page already uses for post-operative constipation ('10 mg oral at night once diet resumed'). It is NOT a colonoscopy or surgical bowel-preparation dose: no bowel-preparation regimen appears anywhere in this bundle. Take bowel-prep dosing from the local protocol or the bowel-prep product's own SPC, not from this field. || VERBATIM §4.2: 'Adults and children over 12 years: 1 to 2 coated tablets (5 - 10 mg) daily before bedtime. Should not be used in children and adolescents under the age of 12 years. It is recommended to start with the lowest dose. The dose may be adjusted up to the maximum recommended dose to produce regular stools. The maximum daily dose should not be exceeded. In the management of constipation, once regularity has been restarted dosage should be reduced and can usually be stopped.' || COURSE LENGTH — §4.4 verbatim: 'As with all laxatives, bisacodyl should not be taken on a continuous daily basis for more than five days without investigating the cause of constipation. Long-term everyday use of stimulant laxatives may harm the intestinal function and should be avoided… This product should only be used if a therapeutic effect cannot be achieved by a change of diet or the administration of bulk forming agents.' This matters on a surgical page where bisacodyl may be started alongside regular opioids. || ELDERLY — §4.2 verbatim: 'No specific information on the use of this product in the elderly is available. Clinical trials have included patients over 65 years and no adverse reactions specific to this age group have been reported.' || SUPPOSITORY, FOR THE RECORD ONLY — the US cross-check label ('Walgreens Gentle Laxative') states verbatim: 'adults and children 12 years of age and older 1 suppository once daily'. Its fetched text nowhere gives the suppository strength, so this count is not publishable as a dose. || NOTE that the SPC does name BHPM, but only in §4.6 and only in the context of lactation: 'neither the active moiety of bisacodyl (BHPM or bis-(p-hydroxyphenyl)-pyridyl-2-methane) nor its glucuronides are excreted into the milk of healthy lactating females.'

Paediatric dose

Route: Oral (coated tablets)
Frequency: Once daily before bedtime — children over 12 years take the adult dose.
NOT WEIGHT-BASED AND NOT LICENSED UNDER 12 YEARS in the primary source, so dosePerKg is null and the weight calculator is deliberately left unset. §4.2 verbatim: 'Adults and children over 12 years: 1 to 2 coated tablets (5 - 10 mg) daily before bedtime. Should not be used in children and adolescents under the age of 12 years.' §4.4 repeats: 'Should not be used in children and adolescents under the age of 12 years.' Children over 12 therefore take the adult dose above. || The US cross-check label in this bundle does carry a paediatric direction for a SUPPOSITORY — verbatim: 'adults and children 12 years of age and older 1 suppository once daily children 6 to under 12 years 1/2 suppository once daily children under 6 years do not use' — but its fetched text nowhere states the suppository strength, so that count cannot be converted into a milligram dose and is NOT published here. US OTC labelling may also differ from UK labelling. || Verify any paediatric dose against a children's formulary. || The product 'should not be used in children and adolescents under the age of 12 years'. The page also holds the prose string 'Fixed dose by age' in paedDose.dosePerKg — that field feeds a weight calculator and must be a number or null, so it has been set to null here.

Dose adjustments

Renal

Not stated — no renal-impairment dose adjustment appears in any fetched section (§4.2, §4.3, §4.4, §4.6, §4.8). §4.4 does carry a renal caution that is about stopping the drug, not adjusting it: 'In patients suffering from fluid loss where dehydration may be harmful (e.g. renal insufficiency, elderly patients) bisacodyl should be discontinued and only be restarted under medical supervision.'

Hepatic

Not stated — no hepatic-impairment dosing or adjustment statement appears in any fetched section of this SPC (§4.2, §4.3, §4.4, §4.6, §4.8).

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Ileus — §4.3 verbatim: 'Bisacodyl Laxative Tablets are contraindicated in patients with ileus, intestinal obstruction, acute abdominal conditions including appendicitis, acute inflammatory bowel diseases, and severe abdominal pain associated with nausea and vomiting which may be indicative of the aforementioned severe conditions.'
  • Intestinal obstruction (§4.3)
  • Acute abdominal conditions including appendicitis (§4.3)
  • Acute inflammatory bowel diseases (§4.3)
  • Severe abdominal pain associated with nausea and vomiting, which may indicate any of the above (§4.3)
  • Severe dehydration — §4.3: 'Bisacodyl Laxative Tablets are also contraindicated in severe dehydration…'
  • Known hypersensitivity to bisacodyl or any other component of the product (§4.3)
  • Hereditary conditions incompatible with an excipient — §4.3: 'In case of hereditary conditions that may be incompatible with an excipient of the product… the use of the product is contraindicated.' §4.4 names them: 'Bisacodyl Laxative Tablets contain a small amount of lactose and sucrose in each tablet. Patients with rare hereditary problems of fructose intolerance, galactose intolerance, total lactase deficiency, glucose-galactose malabsorption or sucrase-isomaltase insufficiency should not take this medicine.'
  • Not a contraindication but a licence restriction (§4.2 and §4.4): 'Should not be used in children and adolescents under the age of 12 years.'

Side effects

  • Common: abdominal cramps, abdominal pain, diarrhoea and nausea — §4.8: 'The most commonly reported adverse reactions during treatment are abdominal pain and diarrhoea.'
  • Uncommon: dizziness
  • Uncommon: haematochezia (blood in stool), vomiting, abdominal discomfort, anorectal discomfort
  • Rare: syncope — §4.8: 'Dizziness and syncope occurring after taking bisacodyl appear to be consistent with a vasovagal response (e.g. to abdominal spasm, defaecation).'
  • Rare: anaphylactic reactions, angioedema, hypersensitivity
  • Rare: dehydration
  • Rare: colitis including ischaemic colitis — §4.4 adds: 'There have been isolated reports of abdominal pain and bloody diarrhoea occurring after taking bisacodyl. Some cases have been shown to be associated with colonic mucosal ischaemia.'
  • §4.4: 'Prolonged excessive use may lead to fluid and electrolyte imbalance and hypokalaemia. Intestinal loss of fluids can promote dehydration. Symptoms may include thirst and oliguria.'

Monitoring

  • Course length — §4.4 verbatim: 'As with all laxatives, bisacodyl should not be taken on a continuous daily basis for more than five days without investigating the cause of constipation.'
  • Cause of constipation — §4.4: 'Long-term everyday use of stimulant laxatives may harm the intestinal function and should be avoided. If laxatives are needed every day the cause of the constipation should be investigated.'
  • Fluid and electrolyte status with prolonged excessive use — §4.4: 'Prolonged excessive use may lead to fluid and electrolyte imbalance and hypokalaemia.'
  • Patients in whom dehydration may be harmful — §4.4: 'In patients suffering from fluid loss where dehydration may be harmful (e.g. renal insufficiency, elderly patients) bisacodyl should be discontinued and only be restarted under medical supervision.'
  • Rectal bleeding — §4.4: 'Patients may experience haematochezia (blood in stool) that is generally mild and self-limiting. If the symptoms worsen during the use of the medicinal product, a doctor or pharmacist should be consulted.'
  • Abdominal pain with bloody diarrhoea — §4.4 links isolated reports to colonic mucosal ischaemia; consider ischaemic colitis.
  • Response and step-down — §4.2: 'In the management of constipation, once regularity has been restarted dosage should be reduced and can usually be stopped.'

Clinical monograph

How it works

It stimulates the enteric nerves of the colonic wall to increase peristalsis and promotes fluid and electrolyte accumulation in the bowel lumen.

Prescribing in practice

  • Do not use where intestinal obstruction, ileus, or undiagnosed acute abdominal symptoms are suspected, as stimulant laxatives can be harmful in these settings.
  • Avoid prolonged or excessive use, which may lead to fluid and electrolyte disturbance, particularly hypokalaemia.
  • Suppositories act rapidly and may cause local rectal irritation, while oral tablets should be swallowed whole and not taken with milk or antacids.

Monitoring

Monitor for adequate bowel response, abdominal pain, and electrolyte disturbance with prolonged or high-dose use.

Counselling the patient

  • Oral tablets usually work overnight, while suppositories work within an hour.
  • Drink plenty of fluids and use it only for short periods.
  • Stop and seek advice if you develop severe abdominal pain.

Evidence & guidelines

Bisacodyl is a long-established stimulant laxative widely used for constipation and bowel preparation, with efficacy supported by clinical experience.

Reference: Dulcolax SPC; NICE NG90; ERAS Society Guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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