MiraLAX and Dulcolax Together: Safety and Efficacy
Yes, it is safe to take MiraLAX (polyethylene glycol) and Dulcolax (bisacodyl) together, and this combination is often recommended for persistent constipation when either agent alone is insufficient. 1
Mechanism of Action and Rationale for Combination
These medications work through different mechanisms:
- MiraLAX (polyethylene glycol): An osmotic laxative that draws water into the intestinal lumen to soften stool and increase bowel movements 1
- Dulcolax (bisacodyl): A stimulant laxative that increases intestinal motility by promoting intestinal contractions 1, 2
Evidence Supporting Combined Use
The National Comprehensive Cancer Network (NCCN) Palliative Care guidelines specifically mention using both agents together for managing constipation:
- If constipation persists despite initial treatment, adding bisacodyl 10-15 mg, 2-3 times daily is recommended 1
- For ongoing constipation, oral polyethylene glycol (MiraLAX) can be added to bisacodyl to achieve the goal of one non-forced bowel movement every 1-2 days 1
Research has shown these medications have complementary effects on colonic motility:
- Bisacodyl significantly increases high-amplitude propagating contractions (HAPCs) 2
- Polyethylene glycol increases low-amplitude long-distance propagating contractions 2
Dosing Recommendations
When using both medications together:
- MiraLAX: Standard dose is 17g (about 1 heaping tablespoon) dissolved in 8 ounces of water once daily
- Bisacodyl: 10-15 mg daily, which can be divided 2-3 times per day 1
Clinical Applications
This combination is particularly useful in:
- Persistent constipation not responding to a single agent 1
- Opioid-induced constipation 1
- Preparation for colonoscopy (though specific protocols may vary) 3, 4
Precautions and Contraindications
While generally safe when used together, avoid this combination in patients with:
Bisacodyl has been associated with rare occurrences of ischemic colitis 1, so monitor for severe abdominal pain or bloody stools.
Monitoring
When using this combination:
- Monitor for adequate hydration
- Assess for bowel movement frequency and consistency
- Watch for signs of excessive effect (diarrhea, cramping)
- Adjust dosing as needed to achieve goal of one non-forced bowel movement every 1-2 days 1
If constipation persists despite this combination, consider other options such as magnesium citrate, lactulose, or consultation with a gastroenterologist 1.