What is the recommended dose of Miralax (polyethylene glycol) for relieving extreme constipation?

Recommended Dosage of Miralax for Extreme Constipation

For extreme constipation, the recommended dose of Miralax (polyethylene glycol 3350) is 17 grams mixed in 8 ounces of liquid once daily. 1

Standard Dosing Regimen

• The FDA-approved dose of polyethylene glycol (PEG) 3350 is 17 grams daily mixed in 8 ounces of liquid for relief of constipation 1
• This standard dose has been shown to be effective for treating constipation with moderate certainty of evidence 1
• Response to PEG has been shown to be durable over 6 months with no evidence of tachyphylaxis (loss of effectiveness over time) 1, 2

For More Severe or Urgent Cases

• For extreme constipation requiring more rapid relief, higher doses may be considered:
  • A 68-gram dose of PEG has been shown to provide effective relief within 24 hours in severely constipated adults 3
  • This higher dose resulted in an average of 2.2 bowel movements within 24 hours compared to 0.5 with placebo 3

Administration Guidelines

• Mix the powder completely in 8 ounces of water or other beverage until dissolved 1
• Take once daily, preferably in the morning 1
• Ensure adequate hydration while taking PEG, as proper fluid intake is essential for effectiveness 1
• Standard doses of fiber supplements are typically taken with 8-10 ounces of fluid, and the same applies to PEG 1

Mechanism of Action and Effectiveness

• PEG is a long-chain polymer of ethylene oxide that acts as an osmotic laxative 1
• It likely increases complete spontaneous bowel movements (CSBMs) per week compared with placebo (mean difference 2.90) 1
• PEG also increases spontaneous bowel movements (SBMs) per week (mean difference 2.30) 1
• Higher rates of individuals meet responder definitions with PEG compared to placebo 1

Side Effects and Precautions

• Common side effects include abdominal distension, loose stool, flatulence, and nausea 1
• Diarrhea was noted more commonly with PEG treatment compared to placebo 1
• There were no significant differences in laboratory findings or serious adverse events between PEG and placebo groups 4
• No significant changes in electrolytes, calcium, glucose, BUN, creatinine, or serum osmolality have been observed with proper use 3

Treatment Duration

• PEG is approved for short-term use for occasional constipation 1
• However, studies have shown it to be safe and effective for treating constipation for periods up to 12 months 2
• For extreme constipation, continue treatment until regular bowel movements are established, then consider tapering to a maintenance dose if needed 1

Special Considerations

• For elderly patients, the same standard dose (17g) has been shown to be both safe and effective 4, 2
• For patients taking constipating medications, PEG at the standard dose has been specifically shown to be effective 4
• A trial of fiber supplement can be considered for mild constipation before PEG use or in combination with PEG 1