ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Stimulant Laxative Pregnancy: Caution — avoid in first trimester; suppository preferred over oral for short-term use if needed.

Bisacodyl

Brand names: Dulcolax

Adult dose

Dose: Oral: 5–10mg at night (acts in 10–12 hours). Rectal suppository: 10mg in the morning (acts in 20–60 minutes).
Route: Oral or rectal
Frequency: Once daily
Max: 10mg oral; 10mg per suppository
Oral: take at night — acts in 10–12 hours. Do not crush or chew (enteric-coated) — do not take within 1 hour of antacids or milk (destroys coating, causing gastric irritation). Suppository: acts within 20–60 minutes — useful when rapid bowel clearance needed.

Paediatric dose

Route: Oral or rectal
Frequency: Once daily
Max: 10mg
BNF for Children: Oral: 4–17 years: 5mg at night. Suppository: 2–9 years: 5mg; 10–17 years: 10mg. Source: BNF for Children 2024.

Dose adjustments

Renal

No dose adjustment required.

Hepatic

No dose adjustment required.

Clinical pearls

  • Enteric-coated tablets must not be crushed or chewed, and must be separated from antacids/milk by 1 hour — coating prevents gastric irritation from bisacodyl.
  • Suppository route preferred when rapid onset required (bowel preparation, post-op constipation, faecal impaction adjunct).
  • Bowel preparation: bisacodyl 10mg oral the evening before colonoscopy followed by macrogol morning of procedure (NICE recommended combination).
  • Long-term stimulant laxative use: no evidence of long-term harm at recommended doses despite historical concerns about cathartic colon.

Contraindications

  • Intestinal obstruction
  • Acute abdomen
  • Severe dehydration
  • Ileus

Side effects

  • Abdominal cramps (common)
  • Diarrhoea (overuse)
  • Rectal irritation (suppository)
  • Electrolyte imbalance (prolonged overuse)
  • Nausea

Interactions

  • Antacids or milk: destroys enteric coating of oral tablet — separate by at least 1 hour
  • Diuretics: additive hypokalaemia risk with overuse

Monitoring

  • Stool frequency
  • Electrolytes (prolonged use)

Reference: BNFc; BNF 90; BSG Bowel Preparation Guidelines; SPC Dulcolax. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Drugs
Pathways