Injectable Weight Loss Medications: A New Option for Obesity Management

New-generation injectable medications, particularly Semaglutide and Tirzepatide, have demonstrated significant weight reduction, making them promising options for obesity management under medical supervision.

Obesity is a condition characterized by increased fat accumulation throughout the body, including both subcutaneous fat and visceral fat (fat around internal organs).
The most accurate way to diagnose total body obesity is by directly measuring body fat percentage, which requires specialized equipment and can be costly. Therefore, in clinical practice, obesity is commonly assessed using the Body Mass Index (BMI), which is considered appropriate for individuals aged 18 years and older. BMI is calculated using the following formula: BMI = weight (kg) / height² (m²)

Body composition classifications for Asian populations differ from international standards.
 

	Asian populations (kg/m2)	International standards (kg/m2)
overweight	23.0-24.9	25.0-29.9
obesity	≥25.0	≥30.0

 
 Obesity is a complex chronic disease that can affect multiple organ systems in the body. It included the risk of health complications, Hypertension, Type 2 diabetes, Cardiovascular diseases, Metabolic dysfunction-associated steatotic liver disease (MASLD), Reproductive system disorders, Osteoarthritis, Respiratory disorders etc.
 
When lifestyle modifications such as dietary changes, increased physical activity, and behavioral therapy fail to achieve meaningful weight loss, medication may be considered. In Asian populations, anti-obesity medications may be initiated in patients with: BMI ≥ 27 kg/m², or BMI ≥ 25.0 kg/m² along with comorbidities such as diabetes, coronary artery disease, hypertension, or dyslipidemia.
 
In Thailand, several medications are used to support weight loss, including Orlistat, Phentermine, Liraglutide, Semaglutide, and Tirzepatide. In recent years, the development of injectable alternatives. Liraglutide is administered subcutaneously once daily, while Semaglutide and Tirzepatide are also subcutaneous injections but offer greater convenience as they are administered only once weekly. The doctor will assess and select the appropriate drug to treat the individual patient.
 
These newer agents, particularly semaglutide and tirzepatide, have shown significant weight reduction and metabolic improvements, making them promising options in the long-term management of obesity.
 

Medication Characteristics

	Semaglutide	Tirzepatide
Mechanism of Action	GLP-1 receptor agonist	Dual GIP and GLP-1 receptor agonist
Effect on Insulin	Weight Loss Effect	Stimulates insulin secretion
Effect on Glucagon	Suppressed glucagon secretion	Suppressed glucagon secretion
Effect on Gastric Motility	Slows gastric emptying	Slows gastric emptying
Effect on Appetite	Suppressed appetite	Suppressed appetite
Weight Loss Effect	Weight reduction	Weight reduction

Tirzepatide, with its added mechanism as a GIP receptor agonist, enhances blood sugar regulation and further suppresses appetite.
 

Advantages of Once-Weekly Injectable Medications

• Convenient to use
• Reduced injection frequency
• Proven to be more effective in weight loss than oral medications in multiple studies

Medications in the GLP-1 receptor agonist group (such as Semaglutide) and GIP/GLP-1 dual agonists (such as Tirzepatide) not only support weight loss but also help regulate blood sugar levels, which is especially beneficial for diabetic patient.
However, these medications are to be prescribed and monitored by a healthcare provider. A healthcare provider will:

• Assess overall health and determine medical indications.
• Screen for contraindications (e.g., patients or family history of medullary thyroid carcinoma (MTC), Multiple Endocrine Neoplasia type 2, or history of allergic reactions to the medication).
• Monitor for precautions and potential complications.
• Adjust dosage individually.
• Observe for side effects (e.g., nausea, vomiting, bloating, diarrhea or constipation).
• Provide ongoing follow-up and treatment monitoring.

References

1. สถาบันวิจัยและประเมินเทคโนโลยีทางการแพทย์ กรมการแพทย์ กระทรวงสาธารณสุข. แนวทางเวชปฏิบัติการป้องกนและดูแลรักษาโรคอ้วน. กรุงเทพฯ: สถาบันวิจัยและประเมินเทคโนโลยีทางการแพทย์ กรมการแพทย์ กระทรวงสาธารณสุข; 2553

2.สุณี เลิศสินอุดม. Glucagon-like peptide 1 receptor agonists for type 2 diabetes mellitus. 2016 [cite 2025 May 07]. Available from: https://ccpe.pharmacycouncil.org/index.php?option=article_detail&subpage=article_detail&id=196

3. Samms RJ, Coghlan MP, Sloop KW. How may GIP enhance the therapeutic efficacy of GLP-1?. Trends in Endocrinology & Metabolism. 2020 Jun 1;31(6):410-21.

4. Jastreboff AM, Aronne LJ, Ahmad NN, Wharton S, Connery L, Alves B, Kiyosue A, Zhang S, Liu B, Bunck MC, Stefanski A. Tirzepatide once weekly for the treatment of obesity. New England Journal of Medicine. 2022 Jul 21;387(3):205-16.

5. Garvey WT, Batterham RL, Bhatta M, Buscemi S, Christensen LN, Frias JP, Jódar E, Kandler K, Rigas G, Wadden TA, Wharton S. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nature medicine. 2022 Oct;28(10):2083-91.

6. UpToDate. Lexi-Drugs Multinational. Orlistat [Internet]. 2025 [cited 2025 May 08]. Available from: https://online.lexi.com/lco/action/doc/retrieve/docid/multinat_f/4669147?cesid=8THiHQVuo1J&searchUrl=%2Flco%2Faction%2Fsearch%3Fq%3Dorlistat%26t%3Dname%26acs%3Dtrue%26acq%3Dorlistat

7. UpToDate. Lexi-Drugs Multinational. Diethylpropion [Internet]. 2025 [cited 2025 May 08]. Available from: https://online.lexi.com/lco/action/doc/retrieve/docid/multinat_f/4668301?cesid=8ZKp3mov8gP&searchUrl=%2Flco%2Faction%2Fsearch%3Fq%3DDiethylpropion%26t%3Dname%26acs%
3Dfalse%26acq%3DDiethylpropion

8. UpToDate. Lexi-Drugs Multinational. Phentermine [Internet]. 2025 [cited 2025 May 08]. Available from: https://online.lexi.com/lco/action/doc/retrieve/docid/multinat_f/4669678?cesid=3wcmA5bou1e&searchUrl=%2Flco%2Faction%2Fsearch%3Fq%3DPhentermine%26t%3Dname%26acs%3Dfalse%26acq%
3DPhentermine

9. UpToDate. Lexi-Drugs Multinational. Liraglutide [Internet]. 2025 [cited 2025 May 08]. Available from: https://online.lexi.com/lco/action/doc/retrieve/docid/multinat_f/4668835?cesid=2ITRvoz5qRi&searchUrl=%2Flco%2Faction%2Fsearch%3Fq%3Dliraglutide%26t%3Dname%26acs%3Dtrue%26acq%3Dlira#use

10. UpToDate. Lexi-Drugs Multinational. Semaglutide [Internet]. 2025 [cited 2025 May 08].
Available from: https://online.lexi.com/lco/action/doc/retrieve/docid/multinat_f/6577214?cesid=0THudYa7QmP&searchUrl=%2Flco%2Faction%2Fsearch%3Fq%3Dsemaglutide%26t%3Dname%26acs%3Dtrue%26acq%3Dsem

11. UpToDate. Lexi-Drugs Multinational. Phentermine [Internet]. 2025 [cited 2025 May 08]. Available from: https://online.lexi.com/lco/action/doc/retrieve/docid/multinat_f/7224069?cesid=aK4wZMwA9S1&searchUrl=%2Flco%2Faction%2Fsearch%3Fq%3Dtirzepatide%26t%3Dname%26acs%3Dtrue%26acq%3Dtir

12. U.S. Food and Drug Administration. Wegovy® (semaglutide) injection [Internet]. 2023 [cited 2025 May 07]. Available from: https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/215256s007lbl.pdf

13. U.S. Food and Drug Administration. Mounjaro® (tirzepatide) injection [Internet]. 2023 [cited 2025 May 07]. Available from: https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/215866s000lbl.pdf

By the  Pharmacy Services