Restoralax (Polyethylene Glycol) for Adult Constipation
The American Gastroenterological Association and American College of Gastroenterology strongly recommend polyethylene glycol (PEG) as first-line pharmacological therapy for chronic idiopathic constipation in adults, with moderate-quality evidence supporting its efficacy and durability over 6 months. 1, 2
Recommended Dosing Approach
Standard maintenance dosing: Use 17 grams (approximately one heaping tablespoon) of PEG 3350 dissolved in 240 mL (8 oz) of water once daily. 3 This typically produces a bowel movement within 1-3 days. 3
For acute "bowel clean-out" or rapid relief: A higher single dose of 68 grams dissolved in 500 mL of flavored water provides safe and effective relief within 24 hours in constipated adults. 4 This dose produces an average of 2.2 bowel movements within 24 hours, with 50% of patients reporting complete evacuation after the first bowel movement and 100% after the second. 4 The median time to first bowel movement is approximately 14.8 hours. 4
Clinical Implementation Strategy
Step 1 - Initial therapy: Start with PEG as first-line treatment, particularly if fiber supplementation has failed or is not tolerated. 1, 2 For mild constipation, you may trial fiber (specifically psyllium) before or in combination with PEG, though this is optional. 1
Step 2 - Adequate trial period: Continue PEG for at least 4-6 weeks before declaring treatment failure, as response has been shown to be durable over 6 months. 1, 2
Step 3 - Escalation if inadequate: If PEG fails after 4-6 weeks, add or switch to prescription secretagogues (linaclotide 145 mcg once daily or plecanatide), both of which receive strong recommendations. 2
Step 4 - Alternative mechanism: Consider prucalopride (a serotonin type 4 agonist) if secretagogues fail or are not tolerated, as it works through a different mechanism. 2
Comparative Efficacy
PEG demonstrates superior efficacy compared to other osmotic laxatives. 5 It is more effective than lactulose for treating functional constipation in both short-term and long-term use. 5 PEG is as effective as enemas for fecal impaction while avoiding hospital admission and being better tolerated by patients. 5
Safety Profile and Side Effects
Common side effects include abdominal distension, loose stool, flatulence, and nausea, which are generally well-tolerated. 1 No electrolyte disturbances, changes in calcium, glucose, BUN, creatinine, or serum osmolality occur with PEG use. 4
Critical safety advantage: Unlike magnesium-based laxatives (milk of magnesia), PEG has no renal contraindications and does not cause hypermagnesemia. 2, 6 Magnesium products are contraindicated when creatinine clearance is <20 mL/min. 2
Key Clinical Pitfalls to Avoid
- Inadequate hydration: Encourage adequate fluid intake with PEG use to optimize efficacy. 1
- Premature discontinuation: Do not abandon PEG before a 4-6 week trial, as efficacy improves with continued use. 2
- Unnecessary escalation to stimulants: Bisacodyl and senna should be reserved for short-term use (≤4 weeks) or rescue therapy, not as first-line agents. 2
- Inappropriate enema use: Avoid mineral oil enemas due to risks of perforation, mucosal irritation, and bacterial translocation; PEG is more effective and safer. 6
Cost-Effectiveness Consideration
PEG is recommended as the next step due to its strong evidence base and cost-effectiveness compared to prescription alternatives. 2 It is available over-the-counter, making it accessible for most patients. 1