Bisacodyl - Drug Monograph

Introduction

Bisacodyl is a widely used stimulant laxative medication that belongs to the diphenylmethane derivative class. It is commonly prescribed for the treatment of constipation and for bowel preparation prior to medical procedures. First introduced in the 1950s, bisacodyl remains one of the most frequently recommended over-the-counter and prescription laxatives worldwide due to its predictable efficacy and generally favorable safety profile.

Mechanism of Action

Bisacodyl exerts its laxative effect through direct stimulation of the colonic mucosa. The drug is hydrolyzed by intestinal enzymes to its active metabolite, bis-(p-hydroxyphenyl)-pyridyl-2-methane (BHPM). This active compound stimulates the sensory nerve endings in the colonic mucosa, which initiates peristaltic contractions and promotes bowel motility. Additionally, bisacodyl increases water and electrolyte secretion into the intestinal lumen, resulting in softer stool consistency and facilitated defecation. The drug primarily acts on the large intestine, with onset of action typically occurring within 6-12 hours after oral administration.

Indications

• Treatment of occasional constipation
• Bowel evacuation prior to diagnostic procedures (colonoscopy, radiography)
• Preoperative bowel preparation
• Management of constipation in patients with certain neurological conditions
• Constipation associated with opioid use (adjunct therapy)

Dosage and Administration

• Oral tablets: 5-15 mg once daily (typically 10 mg)
• Rectal suppositories: 10 mg once daily

• Children >6 years: 5 mg orally once daily
• Children 2-11 years: 5 mg rectally once daily
• Children <2 years: Use not recommended without medical supervision

• Renal impairment: No dosage adjustment required
• Hepatic impairment: No dosage adjustment required
• Elderly: Start with lower end of dosing range
• Pregnancy: Category B - generally considered safe for short-term use

Administration guidelines: Oral tablets should be swallowed whole with water, not crushed or chewed. Avoid taking within 1 hour of antacids or dairy products. Rectal suppositories should be inserted pointed end first and retained for 15-20 minutes.

Pharmacokinetics

Contraindications

• Known hypersensitivity to bisacodyl or any component of the formulation
• Acute surgical abdomen
• Appendicitis symptoms
• Acute inflammatory bowel disease
• Intestinal obstruction
• Severe abdominal pain with nausea and vomiting
• Severe dehydration

Warnings and Precautions

• Prolonged use may lead to laxative dependence and electrolyte abnormalities
• Risk of hypokalemia with chronic use
• Use with caution in patients with pre-existing electrolyte imbalances
• Rectal administration may cause local irritation or burning sensation
• Not recommended for children under 2 years without medical supervision
• Avoid use in patients with rectal bleeding or anal fissures
• Discontinue use if severe cramping or rectal bleeding occurs

Drug Interactions

• Antacids: Concurrent administration may cause premature dissolution of enteric coating, leading to gastric irritation
• Diuretics: Increased risk of hypokalemia when used concomitantly
• Corticosteroids: Enhanced risk of potassium depletion
• Digoxin: Hypokalemia may potentiate digoxin toxicity
• Other laxatives: Increased risk of electrolyte disturbances with combination therapy
• Milk and dairy products: May cause premature dissolution of enteric coating

Adverse Effects

• Abdominal cramping
• Abdominal discomfort
• Nausea
• Diarrhea
• Rectal irritation (with suppository form)

• Electrolyte abnormalities (hypokalemia, hypocalcemia)
• Dizziness
• Weakness
• Allergic reactions (rash, pruritus)
• Rectal burning sensation
• Fainting episodes (with vigorous peristalsis)

• Severe electrolyte disturbances
• Stevens-Johnson syndrome (very rare)
• Anaphylactic reactions (very rare)
• Ischemic colitis (case reports)

Monitoring Parameters

• Bowel movement frequency and consistency
• Electrolyte levels with prolonged use (potassium, sodium, calcium)
• Hydration status
• Signs of abdominal distress or obstruction
• Patient weight with chronic use
• Signs of laxative abuse or dependence
• Rectal examination if persistent symptoms with suppository use

Patient Education

• Use only as directed for short-term relief of constipation
• Swallow tablets whole with water; do not crush or chew
• Avoid taking within 1 hour of antacids or dairy products
• Expect bowel movement within 6-12 hours after oral dose
• Report severe abdominal pain, rectal bleeding, or no bowel movement after use
• Increase fluid intake and dietary fiber to prevent constipation recurrence
• Do not use for more than 7 days without medical advice
• Store at room temperature away from moisture
• Rectal suppositories should be retained for 15-20 minutes for optimal effect
• Seek medical attention if symptoms persist beyond 1 week

References

1. American Society of Health-System Pharmacists. AHFS Drug Information. Bethesda, MD: ASHP; 2023. 2. Brenner DM, Shah M. Chronic Constipation. Gastroenterol Clin North Am. 2016;45(2):205-216. 3. Müller-Lissner SA, Kamm MA, Scarpignato C, Wald A. Myths and misconceptions about chronic constipation. Am J Gastroenterol. 2005;100(1):232-242. 4. Ford AC, Moayyedi P, Lacy BE, et al. American College of Gastroenterology monograph on the management of irritable bowel syndrome and chronic idiopathic constipation. Am J Gastroenterol. 2014;109 Suppl 1:S2-S26. 5. Prescribing Information. Dulcolax® (bisacodyl) tablets and suppositories. Bayer HealthCare Pharmaceuticals Inc. 6. Lee-Robichaud H, Thomas K, Morgan J, Nelson RL. Lactulose versus Polyethylene Glycol for Chronic Constipation. Cochrane Database Syst Rev. 2010;(7):CD007570. 7. World Gastroenterology Organisation Global Guidelines. Constipation: A Global Perspective. 2010. 8. FDA Drug Safety Communication: FDA warns about possible harm from exceeding recommended dose of over-the-counter sodium phosphate products to treat constipation. 2014.