Quick Overview and Official Indications

Key Distinction: Saxenda, Wegovy and Mounjaro are officially approved specifically for "weight management." Ozempic is a diabetes medication, but its active ingredient is the same as Wegovy's (semaglutide), only the dosage differs. Mounjaro's dual mechanism makes it stand out in terms of weight loss efficacy.

In-Depth Analysis of Pharmacological Mechanisms

These four drugs all belong to the "incretin mimetics" class, but they target different pathways.

1. Saxenda (Liraglutide) Saxenda [1]
• Single-Target Action: A GLP-1 (Glucagon-Like Peptide-1) receptor agonist.  

• Mechanism:

• Brain: Acts on appetite centers in the hypothalamus, increasing satiety and reducing hunger.  
• Gastrointestinal Tract: Slows gastric emptying, keeping food in the stomach longer, thereby promoting a feeling of fullness.  
• Pancreas: Stimulates insulin secretion and suppresses glucagon when blood sugar is high, thus lowering blood glucose. 

2. Wegovy & Ozempic (Semaglutide） [2]

• Single-Target Action: Also a GLP-1 receptor agonist, but with a different chemical structure from liraglutide. 
• Mechanism: Similar to Saxenda, but semaglutide has a longer half-life in the body (about one week), allowing for once-weekly injection. It has a stronger binding affinity to the GLP-1 receptor, and its blood sugar-lowering and weight loss effects are generally considered superior to liraglutide.

3. Mounjaro (Tirzepatide)
   • Dual-Target Action: The world's first GIP (Glucose-dependent Insulinotropic Polypeptide) and GLP-1 receptor dual agonist. 
   • Mechanism:[3]

• Simultaneously activates both GLP-1 and GIP receptors. GIP is another incretin hormone that, when used alone, has modest weight loss effects, but when combined with GLP-1, produces a synergistic effect.  

Believed to suppress appetite more effectively, increase energy expenditure, and improve pancreatic beta-cell function. This "twin attack" mechanism is key to its superior weight loss performance in clinical trials.  

[1] "Liraglutide, a GLP-1 analog, reduces body weight through decreased energy intake by mechanisms involving inhibition of appetite and gastric emptying." - Knudsen LB, et al. J Pharmacol Exp Ther. 2010.

[2] "Semaglutide is an analog of human GLP-1... it activates the GLP-1 receptor, which increases insulin secretion, decreases glucagon secretion, slows gastric emptying, and decreases appetite." - Lau J, et al. Drugs. 2015.

[3] Reference: "The rationale for the dual agonism approach is that GIP... may amplify the effects of GLP-1 receptor agonists on body weight and glycemic control." - Frias JP, et al. Lancet. 2018.

Comprehensive Comparison Table

How to Choose? Pros, Cons, and Suitable Users

Saxenda (Liraglutide)

• Pros: Long time on the market, extensive safety data; for those who cannot tolerate the side effects of once-weekly medications, daily injections allow for more flexible dose adjustment.
• Cons: Relatively weaker weight loss effect; daily injections are less convenient and easier to forget.
• Suitable for: Those new to weight-loss injections, or with a relatively limited budget, who don't mind daily injections.

Wegovy (Semaglutide)

• Pros: Significant weight loss effect; once-weekly injection offers high convenience; officially approved specifically for weight management.
• Cons: High cost; frequently faces global supply shortages; side effects can be stronger than Saxenda.
• Suitable for: Those seeking significant weight loss and medication convenience, with sufficient budget.

Mounjaro (Tirzepatide)

• Pros: Currently the most effective drug for weight loss; once-weekly injection; dual mechanism may offer better metabolic improvements.
• Cons: Highest cost; not yet officially approved for weight loss in many regions (requires "off-label" use); side effect incidence and intensity may be higher.
• Suitable for: Patients where other drugs have not yielded ideal results, or who require highly potent weight loss effects (must be used under strict medical supervision).

Ozempic (Semaglutide)

• Pros: Same active ingredient as Wegovy, with significant effects; once-weekly injection.
• Cons: Not officially approved for weight loss; dosing is designed primarily for diabetics, with a lower maximum dose than Wegovy.
• Suitable for: Obese patients with Type 2 Diabetes, or as an alternative when Wegovy is unavailable.

Important Considerations and Conclusion

1. Prescription Medications: All of these drugs are prescription-only and must be prescribed by a doctor after evaluation. A physician will determine the most suitable medication based on your BMI, health status, presence of diabetes, and other complications.
2. Not a Magic Shot: These medications must be combined with lifestyle changes, including a healthy diet and regular exercise, to achieve the best results and maintain them after discontinuation.[1]
3. Side Effect Management: Gastrointestinal side effects are very common. Following the doctor's instructions to start at a low dose and "titrate up" gradually helps the body adapt and reduces discomfort.
4. Black Box Warning: All these drugs have shown a risk of thyroid C-cell tumors (including medullary thyroid carcinoma) in animal studies. Although the relevance in humans is not yet clear, they are contraindicated in patients with a personal or family history of medullary thyroid carcinoma. [Refer to respective FDA Labels above]
5. Potential for Pancreatitis: Use of GLP-1 receptor agonists has been associated with an increased risk of acute pancreatitis. Patients should be monitored for severe abdominal pain.[2]
6. Cost and Accessibility: These drugs are expensive, and whether insurance covers them (usually only for patients meeting the indicated criteria) is a major consideration. Furthermore, global supply shortages also affect drug accessibility.

[1] Reference: "Comprehensive lifestyle intervention... is the cornerstone of obesity management and should be combined with anti-obesity medications." - Garvey WT, et al. Endocr Pract. 2016.

[2] Reference: "Use of GLP-1 based therapies... was associated with an increased risk of pancreatitis." - Li L, et al. JAMA Intern Med. 2022.

Conclusion

Choosing which weight-loss injection is right for you is a personalised decision that requires in-depth discussion with your doctor.

• For the strongest effect and tolerance of potential side effects, Mounjaro (Tirzepatide) is the current preferred choice.
• Among officially approved weight management drugs, Wegovy (Semaglutide) offers an excellent balance of efficacy and convenience.
• Saxenda (Liraglutide), as an established medication, remains a reliable choice, especially for those who need the flexibility of daily dosing.
• Ozempic (Semaglutide) is a primary choice for diabetics and serves as an alternative to Wegovy for weight loss alone.

Ultimately, no single drug is suitable for everyone. Thoroughly communicating with your doctor, understanding the pros and cons of each medication, and establishing sustainable healthy lifestyle habits are the keys to successful long-term weight management