MiraLAX (Polyethylene Glycol 3350) for Adult Constipation
Polyethylene glycol (PEG) 3350 (MiraLAX) at a dose of 17 grams once daily dissolved in 4-8 ounces of liquid is the recommended first-line pharmacological treatment for adult constipation. 1
Dosing and Administration
- Standard dose: 17 grams (one heaping tablespoon) daily dissolved in 4-8 ounces of water, juice, soda, coffee, or tea 1, 2
- Timing: Can be taken at any time of day, with or without food
- Duration: Most effective when used for 1-2 weeks; should not be used longer than 2 weeks unless directed by a physician 2
- Onset of action: First bowel movement typically occurs within 2-4 days, though individual results may vary 2
Efficacy
- PEG 3350 has demonstrated superior efficacy compared to placebo in multiple clinical trials 3, 4
- In a 6-month study, 52% of patients using PEG 3350 achieved treatment success versus only 11% with placebo 3
- A recent analysis using FDA endpoints showed 42% of patients achieved ≥3 complete spontaneous bowel movements per week with PEG 3350 compared to 13% with placebo 4
Mechanism of Action
PEG 3350 works as an osmotic laxative by retaining water in the stool, which softens the stool and increases the frequency of bowel movements 2. Unlike stimulant laxatives, it does not stimulate intestinal motility directly.
Patient Selection and Special Populations
- Suitable for most adults with constipation
- Effective in elderly patients 3, 5
- Particularly useful for medication-induced constipation, with 78.3% success rate versus 39.1% for placebo 5
- For opioid-induced constipation, PEG 3350 is recommended as part of a prophylactic bowel regimen 6
Clinical Considerations and Cautions
PEG 3350 should not be used by:
- Children (unless prescribed by a physician)
- Pregnant women (unless prescribed by a physician)
- Patients with symptoms of bowel obstruction (nausea, vomiting, abdominal pain or distention)
- Patients with known allergies to polyethylene glycol 2
Potential side effects:
Monitoring and Follow-up
- Monitor for:
- Frequency and consistency of bowel movements
- Relief of constipation symptoms
- Side effects 1
- Discontinue after several satisfactory bowel movements 2
- If unusual cramps, bloating, or diarrhea occur, consult a physician 2
Combination Therapy
- PEG may be used in combination with fiber supplements 1
- For opioid-induced constipation, a stimulant laxative may be added if PEG alone is insufficient 6
- Bulk laxatives such as psyllium are not recommended for opioid-induced constipation 1
When to Refer
- Patients who respond well to PEG treatment typically do not require specialist referral 1
- Consider referral for patients over 45 years with:
- Atypical symptoms
- Short history
- Persistent symptoms despite adequate treatment 1
Higher Doses for Severe Constipation
- For severe cases or fecal impaction, up to 8 packets of 13.8g PEG 3350 in 4-6 hours may be used under medical supervision 1
After completing successful treatment with PEG 3350, lifestyle modifications including adequate dietary fiber, fluid intake, and regular exercise should be implemented to maintain regular bowel habits.