What is the first‑line therapy for retatrutide‑induced constipation?

First-Line Treatment for Retatrutide-Induced Constipation

Start polyethylene glycol (PEG) 17 grams once daily as first-line therapy for retatrutide-induced constipation, titrating the dose to achieve one non-forced bowel movement every 1–2 days. 1, 2

Initial Assessment Before Treatment

Before initiating laxative therapy, perform a digital rectal examination to rule out fecal impaction 1. If impaction is present, treat with mineral oil or warm water enemas first 3. Review all medications to identify and discontinue other constipating agents when feasible 1.

First-Line Pharmacological Approach

• Polyethylene glycol (PEG) 17 grams once daily is the preferred initial agent, taken with 8 oz of water 1, 2
• PEG is superior to placebo for increasing bowel movement frequency and stool weight, with FDA-approved efficacy data 2
• Titrate the dose upward based on response; abdominal discomfort is the most common side effect 1
• The goal is one non-forced bowel movement every 1–2 days, not necessarily daily bowel movements 1

Critical Pitfall: Avoid Docusate

Do not use docusate (Colace) as it lacks efficacy for medication-induced constipation 1. Evidence demonstrates that adding docusate to other laxatives provides no additional benefit 1.

Second-Line: Add a Stimulant Laxative

If constipation persists after 2–4 weeks of PEG therapy:

• Add bisacodyl 10–15 mg once daily (oral tablet or rectal suppository) 4, 1
• Alternative: senna 2 tablets every morning, maximum 8–12 tablets per day 4, 1
• These stimulant laxatives are equally appropriate as first-line therapy, particularly for GLP-1 agonist-induced constipation 1

Lifestyle Modifications (Adjunctive)

• Increase fluid intake to at least 2 liters daily 4, 1
• Increase physical activity when appropriate 4, 1
• Avoid supplemental fiber (psyllium/Metamucil) as it is ineffective for medication-induced constipation and may worsen symptoms 4, 1

Third-Line: Prokinetic Agent

If constipation remains refractory despite PEG plus stimulant laxative:

• Consider metoclopramide 10–20 mg, 2–3 times daily as a prokinetic agent 4, 1
• This is particularly relevant for retatrutide because GLP-1 receptor agonists slow gastric emptying, creating a gastroparesis component 1

Fourth-Line: Prescription Secretagogues

For persistent constipation unresponsive to standard laxatives after 3 months:

• Linaclotide 290 µg once daily on an empty stomach (≥30 minutes before first meal) 1
• Alternative: lubiprostone 8 µg twice daily with food 4, 1
• Alternative: plecanatide 3 mg daily 1

Monitoring and Reassessment

• Reassess efficacy after 3 months of any therapy 1
• Discontinue ineffective treatments rather than continuing them indefinitely 1
• If constipation persists, reassess for fecal impaction or bowel obstruction before escalating therapy 4, 1

Context: Retatrutide and Gastrointestinal Side Effects

Retatrutide is a triple-hormone-receptor agonist (GIP/GLP-1/glucagon) where gastrointestinal adverse events are the most common side effects, are dose-related, and mostly mild to moderate in severity 5. The constipation mechanism is similar to other GLP-1 agonists, which slow gastric emptying and intestinal transit.