What are the side effects of Mounjaro (tirzepatide)?

Side Effects of Mounjaro (Tirzepatide)

Mounjaro (tirzepatide) primarily causes gastrointestinal side effects, with nausea, diarrhea, and vomiting being the most common adverse reactions, occurring in up to 49% of patients depending on dosage. 1

Common Gastrointestinal Side Effects

Gastrointestinal effects are dose-dependent and typically most pronounced during dose escalation:

• Nausea: Affects approximately 31% of patients 1
• Diarrhea: Occurs in about 23% of patients 1
• Vomiting: Reported by 12% of patients 1
• Constipation: Affects around 5% of patients 1
• Abdominal pain: Experienced by approximately 5% of patients 1
• Decreased appetite: Common side effect that contributes to weight loss 2
• Dyspepsia: Reported in some patients 2

These gastrointestinal effects increase with higher doses, with overall GI adverse events occurring in 39% of patients on 5mg, 46% on 10mg, and 49% on 15mg doses 3.

Cardiovascular Effects

• Increased heart rate: May occur in some patients 1
• Low risk of major adverse cardiovascular events: Studies show no increased risk 4

Other Potential Side Effects

• Injection site reactions: Rare, occurring in less than 1% of patients 1
• Hypoglycemia:
  • Mild hypoglycemia (blood glucose <70 mg/dL) occurs in up to 22.6% of patients, most commonly with the 10mg dose 3
  • Severe hypoglycemia is rare (≤1%) 3

Rare but Serious Side Effects

• Acute pancreatitis: Extremely rare (≤1%) but has been reported 3, 5
• Cholelithiasis and cholecystitis: Very rare (≤1%) 3
• Severe gastrointestinal disorders: Including severe constipation and intestinal obstruction 1
• Appendicitis: Emerging case reports suggest a possible association 6
• Acute kidney injury: Risk may be increased when initiating or increasing dose in patients with renal disease 1

Special Warnings and Precautions

• Thyroid C-cell tumors: Black box warning based on rodent studies, though human relevance has not been determined 1
• Contraindicated in patients with:
  • Personal or family history of medullary thyroid carcinoma
  • Multiple endocrine neoplasia syndrome type 2
  • Pregnancy 1

Managing Side Effects

1. Dose titration: Start with lower doses and gradually increase to minimize side effects
2. For nausea: Consider antiemetics like ondansetron before tirzepatide dose
3. For constipation: Increase fiber intake, ensure adequate hydration, consider mild laxatives
4. For diarrhea: Use loperamide as needed and ensure electrolyte replacement
5. For surgical procedures: Consider stopping weekly tirzepatide injections at least one week before elective procedures to minimize aspiration risk due to delayed gastric emptying 1

Monitoring Recommendations

• Regular follow-up to assess side effect burden
• Consider dose reduction rather than discontinuation if benefits outweigh side effects
• Monitor for expected benefits including weight loss and improved glycemic control
• Use caution when initiating or increasing dose in patients with renal disease 1

Most adverse effects are mild to moderate in severity, with severe adverse events being rare. Discontinuation due to adverse events is highest with the 15mg dose (approximately 10% of patients) 3.