Bowel Regimen for Mounjaro (Tirzepatide)-Induced Constipation
Start with polyethylene glycol (PEG) 17 grams once daily as first-line therapy, combined with increased fluid intake and regular physical activity, with the goal of achieving one non-forced bowel movement every 1-2 days. 1, 2
First-Line Approach
- Initiate PEG (polyethylene glycol) 17 grams once daily mixed in 4-8 ounces of beverage as the primary pharmacologic agent 1, 3
- Increase fluid intake, particularly if the patient is in the lowest quartile of daily consumption 1, 4
- Encourage regular physical activity to utilize the gastrocolic reflex 1, 4
- Target one non-forced bowel movement every 1-2 days without abdominal pain or straining 1, 2, 4
Second-Line Options (If PEG Fails After 4 Weeks)
Add a stimulant laxative to the PEG regimen rather than switching agents. 1, 2
- Bisacodyl 5-10 mg once daily can be added to ongoing PEG therapy 1, 2
- Alternative osmotic agents include lactulose, magnesium hydroxide, or magnesium citrate if PEG is not tolerated 5, 1
- Consider fiber supplementation (age + 5 grams per day minimum) only if the patient has adequate fluid intake 1
Management of Impaction
If fecal impaction develops (a particular concern with GLP-1/GIP agonists like tirzepatide):
- Glycerin suppositories for mild impaction 5, 1
- Bisacodyl suppository 10 mg rectally 5, 1
- Manual disimpaction may be necessary in severe cases 5
Critical Pitfalls to Avoid
- Do not use stool softeners (docusate) alone - they lack efficacy as monotherapy and should not be relied upon 1, 2
- Do not add fiber supplementation without ensuring adequate fluid intake - this can worsen constipation 1
- Do not limit PEG to 7 days in chronic constipation - it can be used long-term safely 1
- Rule out colonic ischemia if the patient develops severe abdominal pain, bloody stools, or acute constipation, as this has been reported with tirzepatide 6
Special Considerations for Tirzepatide
Tirzepatide causes constipation in 13-16% of patients as a common gastrointestinal side effect 7, 8. The mechanism relates to delayed gastric emptying and altered gut motility from dual GIP/GLP-1 receptor agonism 8.
- Prophylactic laxatives should be considered at the time of tirzepatide initiation in patients with pre-existing constipation or risk factors 2, 4
- Monitor for severe constipation that could predispose to colonic ischemia, particularly in older patients or those with cardiovascular risk factors 6
- If constipation is severe and refractory, consider dose reduction of tirzepatide in consultation with the prescribing provider 8
Reassessment Strategy
If constipation persists despite the above measures:
- Reassess for medication-induced causes beyond tirzepatide 1, 4
- Evaluate for metabolic causes including hypothyroidism, hypercalcemia, or hypokalemia 4
- Consider abdominal imaging to exclude mechanical obstruction or severe fecal loading 4
- Refer to gastroenterology for consideration of newer agents like linaclotide (guanylate cyclase-C agonist) or lubiprostone (chloride channel activator) if standard therapy fails 5