Bisacodyl
Bisacodyl is a stimulant laxative used for short-term evacuation of the large bowel. Veterinary uses include selected constipation cases and bowel preparation before procedures that require a cleaner colon. Its action is local within the intestine rather than correction of the underlying reason for constipation.
It is therefore better understood as an occasional evacuation aid than as a complete long-term plan for recurrent obstipation or megacolon. The feasibility of moving stool, hydration and the presence of obstruction influence whether stimulation will be useful.
Group
Stimulant laxative
Mechanism of Action
Bisacodyl and its locally active derivative stimulate intestinal mucosal and enteric neural activity, increasing propulsive contractions of the large bowel. Increased colonic movement advances luminal contents toward evacuation rather than physically breaking up every impacted fecal mass.
It also increases fluid and electrolyte accumulation in the colonic lumen, helping soften contents and facilitate passage. The combination of stronger motility and greater luminal fluid produces a cathartic effect.
The detailed mechanism has not been fully defined in veterinary species. The same stimulation can cause cramping or excessive fluid loss, and repeated use does not restore normal neuromuscular function in a severely diseased colon. Mechanical obstruction is not relieved simply by increasing peristaltic force.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Constipation and bowel evacuation | 5 mg/animal | PO | Every 8–24 h | |
| Constipation and bowel evacuation | 5–20 mg/animal | PO | Every 24 h | Enteric-coated tablets must be swallowed intact; short-term use only. |
| Rectal bowel evacuation | 5–15 mg/animal | RECTAL | Equivalent to one to three 5 mg pediatric suppositories; frequency is not specified. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Constipation and bowel evacuation | 5 mg/animal | PO | Every 8–24 h | |
| Constipation and bowel evacuation | 5 mg/animal | PO | Every 24 h | Swallow enteric-coated tablet intact; avoid daily chronic use. |
| Rectal bowel evacuation | 5–15 mg/animal | RECTAL | Equivalent to one to three 5 mg pediatric suppositories; frequency is not specified. |
Indications
- Short-term treatment of selected constipation in dogs and cats.
- Bowel preparation before endoscopic or surgical procedures requiring colonic evacuation, sometimes within a combined cleansing plan.
Contraindications
- Renal disease; avoid prolonged reliance for constipation.
- Intestinal obstruction, unexplained rectal bleeding or risk of bowel perforation.
Interactions
- No veterinary interactions are documented in the supplied material.
Adverse effects
- Abdominal discomfort
- Fluid and electrolyte depletion
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Bisacodyl 5 mg tablet Enteric-coated tablet; do not break or crush. Whole tablets only. | Tablet | 5 mg / tablet | PO |
Monitoring and Administration
Avoid chronic use. Monitor hydration and electrolytes if administration is prolonged.
May be combined with polyethylene glycol electrolyte bowel preparation. Veterinary dose evidence is empirical.
The medium/large-dog tablet-count example is internally inconsistent: one to two 5 mg tablets is 5–10 mg, not the printed 10–15 mg. That inconsistent example is not used for calculation.
Chronic stimulant use may injure myenteric neurons. Store below 30°C.