GASTRO-RESISTANT BISACODYL 5MG TABLET

Indications

• Constipation
• Bowel clearance before radiological procedures and surgery
• Constipation in palliative care

Dosage

Children: Child 2-11 years: 2.5–5 mL of oral suspension once daily at bedtime; Child 12-17 years: 5–10 mL of oral suspension once daily at bedtime.

Adults: 5–15 mg orally at bedtime, or 10 mg rectally as needed.

Mechanism of action

Bisacodyl acts by stimulating the enteric nerves, increasing peristalsis in the colon, and promoting the secretion of water and electrolytes into the intestines, which softens stool and induces defecation.

Pharmacodynamics

The onset of action varies with the route of administration; oral forms typically act within 10 to 12 hours, while rectal administration can produce effects in 20 to 60 minutes. This differential timing is important for managing bowel preparations before procedures.

Pharmacokinetics

Bisacodyl is absorbed in the gastrointestinal tract and is then metabolized into active forms that exert its laxative effect. Its bioavailability and systemic absorption are low, minimizing systemic side effects.

Adverse effects

• Gastrointestinal discomfort
• Nausea
• Haematochezia
• Vomiting
• Colitis
• Dehydration
• Angioedema

Precautions

• Caution with oral use as it is present in breast milk following oral administration.
• Rectal administration is not known to be harmful.

Pregnancy

May be suitable for constipation in pregnancy if a stimulant effect is necessary.

Breast-feeding

Manufacturer advises caution due to presence in breast milk following oral administration.

Storage

Store in a cool, dry place away from direct sunlight.

Formulations

• Oral solution
• Gastro-resistant tablet
• Suppository
• Enema
• Capsule

Mechanism of action

Bisacodyl is deacetylated to the active bis-(p-hydroxyphenyl)-pyridyl-2-methane (BHPM) by an intestinal deacetylase. BHPM can stimulate parasympathetic nerves in the colon directly to increase motility and secretions. Bisacodyl stimulates adenylate cyclase, increasing cyclic AMP, leading to active transport of chloride and bicarbonate out of cells. Sodium ions, potassium ions, and water passively leave the cell; while sodium and chloride ions are unable to be reabsorbed. Water is also be transported from the luminal side of cells into the vasculature by aquaporin 3. Bisacodyl decreases expression of aquaporin 3, preventing water from moving into the vasculature, which may contribute to increased water in the colon. Bisacodyl directly stimulates parasympathetic nerves in the colon, stimulating contraction of longitudinal smooth muscle but not circular smooth muscle. Bisacodyl is a stimulant laxative, ... acting directly on the colonic mucosa-where it stimulates sensory nerve endings to produce parasympathetic reflexes resulting in increased peristaltic contractions of the colon. The contact action of the drug is restricted to the colon, and motility of the small intestine is not appreciably influenced. /Bisacodyl/ increases water retention in the stool by coating surfaces of stool and intestines with a water-immisicible film. Lubricant effect eases passage of contents through intestines. Emulsification of lubricant tends to enhance its ability to soften stool mass. /Laxatives/ Recent studies show that these drugs alter fluid and electrolyte absorption producing net intestinal fluid accumulation and laxation. Some of these drugs may directly stimulate active intestinal ion secretion. Increased concentrations of cyclic 3',5'-adenosine monophosphate (cAMP), occurring in colonic mucosa cells following administration of stimulant laxatives, may alter the permeability of these cells and mediate active ion secretion thereby producing net fluid accumulation and laxative action. /Stimulant Laxatives/ Bisacodyl caused dose-dependent contractions in isolated guinea pig ileum & taenia coli which was not prevented by atropine or pheniramine. It prevented acetylcholine- & histamine-induced contractions. Bisacodyl-induced contractions were not caused by a decrease in endogenous cyclic amp level. However, both endogenous cyclic amp & verapamil (a calcium transport inhibitor) inhibited bisacodyl-induced contractions, suggesting site of action on calcium-dependent contractile system of smooth muscle cells. Intestinal secretagogues as well as the laxative, bisacodyl, raise the K+ efflux rate across the mucosal border by 200-300%. Results suggest that laxatives may increase rate of K+ secretion into the colonic lumen by raising the K+ permeability of the mucosal border.

Pharmacodynamics

Patients should be counselled regarding abdominal pain, nausea, vomiting, or a change in bowel function that lasts longer than 2 weeks. It has a wide therapeutic index, as patients can take 5-15 mg orally. Patients taking bisacodyl should be counselled before taking the medication if they are already experiencing abdominal pain, nausea, vomiting, or a change in bowel function lasting longer than 2 weeks. Patients should also be counselled to stop taking the medication if they experience rectal bleeding or no bowel movement in 12 hours.