What is the protocol for treating constipation with MiraLAX (polyethylene glycol)?

MiraLAX (Polyethylene Glycol) Protocol for Constipation

For chronic idiopathic constipation in adults, use MiraLAX (polyethylene glycol/PEG) 17 grams mixed in 8 ounces of liquid once daily, which is the most effective first-line osmotic laxative with strong guideline support and durable efficacy over 6 months. 1

Standard Dosing Protocol

Initial Treatment

• Standard dose: 17 grams of PEG 3350 dissolved in 8 ounces of liquid once daily 1, 2
• Expected onset: Generally produces bowel movement within 1-3 days 2
• Best efficacy typically seen by week 2 of treatment 3
• Response is durable and maintained over 6-12 months of continuous use 1, 4

Dose Adjustments

• For faster relief (within 24 hours): A single dose of 68 grams in 500 mL of flavored water can be used, producing first bowel movement in approximately 14.8 hours 3
• The 68-gram dose provides safe overnight efficacy without causing incontinence, cramps, or diarrhea 3
• Standard maintenance remains 17 grams daily for chronic management 1

Clinical Efficacy Data

PEG demonstrates superior outcomes compared to placebo with moderate-certainty evidence: 1

• Increases complete spontaneous bowel movements by 2.90 per week 1
• Increases spontaneous bowel movements by 2.30 per week 1
• Responder rate 3.13 times higher than placebo (RR 3.13, CI 2.00-4.89) 1
• 454 more patients per 1,000 achieve global symptom relief compared to placebo 1

Implementation Strategy

When to Use PEG as First-Line

• Moderate-to-severe chronic constipation requiring immediate effective treatment 1
• Patients who have failed or cannot tolerate fiber supplementation 1
• Opioid-induced constipation when used alongside stimulant laxatives 1

When to Consider Fiber First

• Mild constipation symptoms 1
• Patients with dietary fiber deficiency 1
• Can be used in combination with PEG if needed 1
• Important caveat: Only psyllium has proven efficacy; avoid wheat bran (especially finely ground powder) as it can decrease stool water content and worsen constipation 1, 5

Fluid Intake Requirements

• Administer each dose with 8-10 ounces of fluid 1
• Focus fluid intake increases on patients in the lowest quartile of daily fluid consumption 1, 5

Expected Side Effects

Common but generally mild-to-moderate gastrointestinal effects: 1, 4

• Abdominal distension 1
• Loose stools 1
• Flatulence 1
• Nausea 1
• Diarrhea (158 more per 1,000 compared to placebo) 1

Safety profile: 4

• No clinically significant changes in electrolytes, calcium, glucose, BUN, or creatinine even with 12 months of continuous use 4
• No evidence of tachyphylaxis (tolerance) with long-term use 4
• Safe in elderly patients (age 65+) with similar efficacy and safety profile 4

Critical Exclusion and Monitoring

Contraindications

• Known or suspected mechanical bowel obstruction 1
• Rule out fecal impaction before initiating treatment, especially if diarrhea accompanies constipation (suggests overflow around impaction) 1

When PEG Fails - Escalation Protocol

1. Reassess for treatable causes: 1

   • Fecal impaction (perform rectal exam, consider abdominal x-ray) 1
   • Bowel obstruction 1
   • Hypercalcemia 1
   • Hypokalemia 1
   • Hypothyroidism 1
   • Diabetes mellitus 1
   • Constipating medications 1

2. Add stimulant laxatives: 1

   • Bisacodyl 10-15 mg daily to three times daily 1
   • Senna (particularly for opioid-induced constipation) 1
   • Magnesium-based products (avoid in renal dysfunction) 1, 5

3. Consider second-line agents for refractory cases: 1

   • Peripherally acting mu-opioid receptor antagonists (methylnaltrexone, naloxegol, naldemedine) for opioid-induced constipation 1
   • Lubiprostone 1
   • Linaclotide 1

Special Populations

Opioid-Induced Constipation

• Use prophylactic stimulant laxative (senna) or PEG 17g twice daily from the start of opioid therapy 1
• Docusate (stool softener) has no proven benefit and is not recommended 1
• If standard laxatives fail, add methylnaltrexone 0.15 mg/kg subcutaneously every other day (maximum once daily) 1

Cancer/Palliative Care Patients

• PEG 17g in 8 oz water twice daily can be used 1
• Goal: One non-forced bowel movement every 1-2 days 1
• Avoid rectal suppositories/enemas in neutropenic or thrombocytopenic patients 1

Elderly Patients

• Same dosing as younger adults (17g daily) 4
• 84-94% treatment success rate in elderly patients 4
• No increased risk of adverse effects or electrolyte disturbances 4

Comparative Effectiveness

PEG is superior to other osmotic laxatives: 6

• More efficacious than lactulose for functional constipation 6
• More effective than magnesium hydroxide (which has only conditional recommendation with very low-quality evidence) 5
• As effective as enemas for fecal impaction while avoiding hospitalization 6
• Better tolerated than fiber supplements (which cause more flatulence) 1