Laxative Management for Constipation in Patients with a Colostomy
For a patient with a colostomy experiencing constipation, use polyethylene glycol (PEG) 17 grams (1 capful) mixed in 8 ounces of water twice daily as the first-line osmotic laxative. 1
Why PEG is the Preferred Choice
The evidence strongly supports PEG as the primary osmotic laxative for constipation management. In patients with chronic constipation, PEG demonstrates:
- Significant increase in complete spontaneous bowel movements (2.90 more per week compared to placebo) 1
- Durable response over 6 months of treatment 1
- Moderate certainty of evidence with strong recommendation status 1
The dosing regimen is straightforward: Start with 17 grams (one capful) dissolved in 8 ounces of liquid once or twice daily, adjusting based on response 2, 1.
Alternative Osmotic Laxatives and Dosing
If PEG is unavailable or not tolerated, consider these alternatives in order:
Second-Line Options:
- Lactulose: 30-60 mL twice to four times daily 2
- Magnesium hydroxide: 30-60 mL once to twice daily 2
- Magnesium citrate: 8 ounces daily 2
Important caveat: Magnesium-containing laxatives should be used cautiously in patients with renal impairment due to risk of hypermagnesemia 3.
Critical Considerations for Colostomy Patients
The management differs significantly from typical constipation because colostomy patients have unique physiological considerations:
What NOT to Do:
- Avoid stimulant laxatives as first-line therapy - These should be reserved for as-needed use only 4
- Do not use bulk-forming laxatives initially - High fiber intake can paradoxically increase problems in colostomy patients by thickening output 5
Initial Conservative Approach:
Before starting pharmacotherapy, implement dietary modifications 6:
- Increase fluid intake to 2-2.5 liters daily (more in hot weather)
- Use isotonic drinks rather than hypotonic fluids (tea, water) which can worsen dehydration
- Consider oral rehydration solution if output exceeds 1 liter daily
- Foods that thicken output: bananas, pasta, rice, white bread, mashed potatoes 5
This conservative approach alone resolves constipation in 60% of colostomy patients 6, making it worth attempting before medication.
When Conservative Measures Fail
If dietary modifications are insufficient after 3 months, proceed with the PEG protocol described above 6. A standardized laxative protocol prevents fecal loading more effectively than ad hoc prescribing (1 episode vs 7 episodes in one trial) 7.
Expected Side Effects of PEG:
- Abdominal distension
- Loose stools
- Flatulence
- Nausea 1
These are generally mild and dose-dependent.
Monitoring and Adjustment
Reassess after starting treatment:
- Goal: 1 non-forced bowel movement every 1-2 days 2
- If inadequate response after adequate trial, consider adding a stimulant laxative (bisacodyl 10-15 mg daily) rather than switching osmotic agents 2
- Monitor for signs of fecal impaction, especially if diarrhea develops (may indicate overflow around impaction) 2
The evidence consistently supports osmotic laxatives, particularly PEG, as first-line pharmacotherapy for constipation in colostomy patients, with dietary modifications attempted first when clinically appropriate.