How to administer Miralax (polyethylene glycol)?

How to Administer Miralax (Polyethylene Glycol)

For adults and children 17 years and older, dissolve 17 grams (one heaping tablespoon or one packet) of Miralax in 4 to 8 ounces of any beverage—cold, hot, or room temperature—and drink once daily. 1

Standard Dosing and Preparation

• Measure 17 grams of powder using the white section marking in the bottle cap or use one pre-measured packet 1
• Mix thoroughly in 4-8 ounces of any liquid (water, juice, coffee, tea) until completely dissolved 1, 2
• Do not drink if clumps remain—ensure powder is fully dissolved before consuming 1
• Timing is flexible—can be taken at any time of day that works best for the patient 1

Important Administration Guidelines

• Do not combine with starch-based thickeners used for swallowing difficulties, as this may affect dissolution 1
• Adequate fluid intake throughout the day enhances effectiveness 3, 4
• For children 16 years and under, consult a physician before use 1

Duration and Efficacy Expectations

• Maximum over-the-counter use is 7 days without physician guidance 1
• Onset of action typically occurs within 24-48 hours, with peak efficacy seen in week 2 of treatment 5
• For chronic constipation, the American Gastroenterological Association strongly recommends PEG with moderate certainty of evidence, and it can be used safely for up to 12 months under medical supervision 3, 6

Dosing Adjustments for Specific Situations

For Chronic Idiopathic Constipation

• Standard dose: 17 grams once daily dissolved in 8 ounces of liquid 3, 1
• If inadequate response after 2-4 days, may increase to 17 grams twice daily (total 34 grams per day) 3, 4
• Goal: Achieve one non-forced bowel movement every 1-2 days 3, 4

For Antipsychotic-Induced Constipation

• Start with 17 grams twice daily (morning and evening) in 8 ounces of water with each dose 4
• Add sennosides 2-3 tablets twice to three times daily if PEG alone is insufficient 4
• Do not use fiber supplements (psyllium, methylcellulose) as they are ineffective and may worsen symptoms in this context 4

For Pediatric Dysfunctional Elimination

• Average effective dose: 0.63 gm/kg body weight daily 7
• Can be mixed with any beverage to improve palatability in children 7
• Monitor for diarrhea, the most common adverse effect (reported in approximately 20% of pediatric patients) 7

Common Pitfalls to Avoid

• Insufficient dissolution: Always ensure powder is completely dissolved before drinking to prevent gastrointestinal discomfort 1
• Premature discontinuation: Many patients experience optimal benefit in week 2 rather than immediately 5
• Inadequate fluid intake: PEG works by sequestering fluid in the bowel; patients must maintain adequate hydration throughout the day 3
• Using with fiber in acute constipation: Fiber supplements require adequate motility to be effective and may worsen symptoms in severe constipation 3

Safety Monitoring

• No clinically significant electrolyte disturbances occur with standard dosing in adults or elderly patients 6
• Elderly patients (age 65+) tolerate PEG well at standard doses without dose adjustment 2, 6
• Hypotonic PEG (without electrolytes, like Miralax) may cause a small decrease in plasma sodium (approximately 1 mmol/L) but this is not clinically significant 2
• Long-term use (up to 12 months) shows no evidence of tachyphylaxis or tolerance 6

Expected Outcomes

• Increases complete spontaneous bowel movements by 2.90 per week compared to placebo 3, 4
• 80-88% of patients report successful treatment with global efficacy assessments 6
• Response is durable over time without loss of effectiveness 3, 6