In this article
Key takeaways
- Mounjaro (tirzepatide) is the world's first dual GIP/GLP-1 agonist
- Average weight loss up to 22.5% of body weight in clinical studies (SURMOUNT-1)
- Approved for type 2 diabetes and obesity in the EU and USA
- Weekly subcutaneous injection
- Side effects mainly gastrointestinal and transient
- Mandatory medical supervision for prescription
What is Mounjaro (tirzepatide)?
Mounjaro is the brand name for tirzepatide, an injectable medication developed by Eli Lilly that represents a major innovation in the treatment of obesity and type 2 diabetes. Unlike other medications such as Ozempic (semaglutide), which act on a single hormonal receptor, tirzepatide is the world's first dual GIP/GLP-1 agonist.
This means it simultaneously activates two hormonal receptors involved in the regulation of metabolism, appetite and blood glucose: the GIP receptor (glucose-dependent insulinotropic polypeptide) and the GLP-1 receptor (glucagon-like peptide-1).
At Clínica Eupnea in Palamós, our endocrinology team closely follows the latest developments in metabolic treatments to offer our patients the best available therapeutic options.
The dual mechanism of action: GIP + GLP-1
What makes tirzepatide unique is its ability to act on two hormonal pathways simultaneously:
GLP-1 action: Similar to medications like semaglutide, it stimulates insulin secretion, suppresses glucagon, slows gastric emptying and reduces appetite by acting on the hypothalamus.
GIP action: This is the key innovation. GIP is an incretin hormone that enhances the effect of insulin, improves adipose tissue sensitivity and may play a role in fat metabolism regulation.
Synergistic effect: The combination of both pathways produces superior results in weight loss and glycaemic control compared with single-pathway agonists.
💡 Why are two receptors better than one?
While GLP-1 reduces appetite and improves insulin secretion, GIP works complementarily by improving insulin sensitivity and optimising fat metabolism. Together, they achieve significantly greater weight loss than either pathway alone.
Clinical results in weight loss
The SURMOUNT clinical trials have demonstrated unprecedented results in the treatment of obesity:
SURMOUNT-1 (2022): In patients with obesity or overweight with comorbidities (without diabetes), tirzepatide achieved:
- 5 mg dose: 15% body weight loss over 72 weeks
- 10 mg dose: 19.5% body weight loss
- 15 mg dose: 22.5% body weight loss
SURMOUNT-2 (2023): In patients with type 2 diabetes and obesity, average weight loss of 14.7% with the maximum dose.
These figures consistently surpass those achieved with semaglutide, positioning tirzepatide as the most effective pharmacological treatment for obesity currently available.
Efficacy in type 2 diabetes
In addition to weight loss, Mounjaro has demonstrated exceptional efficacy in type 2 diabetes control:
SURPASS trials:
- HbA1c reduction: Up to 2.07% reduction, surpassing insulin glargine and semaglutide
- Patients reaching HbA1c <7%: Up to 97%
- Patients reaching normoglycaemia (HbA1c <5.7%): Up to 62%
Additional benefits: Improved insulin sensitivity, blood pressure reduction, improved lipid profile and reduced inflammation markers.
Side effects and safety
The side effect profile of tirzepatide is similar to other GLP-1 agonists:
Gastrointestinal effects (most common):
- Nausea (the most common, especially initially)
- Diarrhoea, constipation, vomiting
- Abdominal pain and dyspepsia
These effects are generally mild to moderate and tend to decrease over time. Gradual dose escalation (starting at 2.5 mg) significantly minimises these symptoms.
Rare but important effects: Pancreatitis, gallbladder problems, allergic reactions and potential risk of thyroid tumours (observed in animals, not confirmed in humans).
Availability in Spain and Europe
Diabetes approval: Mounjaro was approved by the EMA in 2022 for type 2 diabetes. It is already available in Spain with a medical prescription for this indication.
Obesity approval: Tirzepatide as Zepbound was approved by the FDA in the USA in November 2023. In Europe, the obesity approval is pending.
Current situation in Spain:
- Available as Mounjaro for type 2 diabetes (with prescription)
- Pending specific approval for obesity as Zepbound
- Not funded by the Spanish National Health System for weight loss
At Clínica Eupnea, our endocrinology team can assess whether tirzepatide is suitable for your case.
Frequently asked questions
Clinical studies suggest that tirzepatide (Mounjaro) produces significantly greater weight loss than semaglutide (Ozempic). While Ozempic achieves losses of 15-17%, Mounjaro can reach 22.5%. The choice depends on each individual case.
Most patients begin to notice a reduction in appetite during the first few weeks. Significant weight loss typically becomes evident from the second or third month of treatment.
Yes, tirzepatide can be combined with metformin and other oral antidiabetics. Caution should be taken with insulin or sulfonylureas due to the risk of hypoglycaemia.
At Clínica Eupnea in Palamós, our endocrinology team can assess whether tirzepatide is suitable for your case. Contact us to schedule a personalised consultation.
Want to know if Mounjaro is right for you?
Book an appointment with our endocrinologist in Palamós for a personalised assessment.
Make an Appointment