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Adeel Arshad

Authored on 24 January 2024 by Adeel Arshad,

Reviewed 24 January 2024 by Dr Ruch Karunadasa.

Mounjaro vs Wegovy, Mysimba & Saxenda

The new UK weight loss injection medication

Weight Loss Injections: Mounjaro vs Wegovy, Mysimba, Ozempic, Saxenda

There has been a surge in the popularity of weight-loss medicines like Saxenda and Wegovy in recent times, resulting in production shortages, delays, and increased off-label and unlicensed prescriptions. When a particular medication becomes scarce, patients often inquire about alternative drugs that can deliver similar outcomes, typically involving rapid and substantial weight loss.

Several drugs have received MHRA approval for managing obesity and/or diabetes. Many of these, such Wegovy, share a common active ingredient: semaglutide.

However, there are also other active ingredients demonstrating efficacy in weight loss, prompting ongoing studies to determine which ingredient acts faster or more effectively, and why certain medicines prove more impactful for some patients.

Experts below elucidate the distinctions among these trending weight-loss drugs concerning their function, effectiveness, and known side effects.


Active Ingredient: Semaglutide

Found in: Wegovy, Rybelsus. Additionally, compounded Semaglutide, often blended with a base of sodium or acetate plus B12 or L-carnitine, has gained popularity as a more affordable alternative for those unable to access the brand-name medication.

Description: Semaglutide, developed in 2012 and first released for treating type 2 diabetes in 2017. It is administered through various forms such as Ozempic (weekly injection for diabetes), Wegovy (weekly injection for obesity), and Rybelsus (daily tablets for diabetes).

Dosage: Wegovy initiates at 0.25 mg, with the option to increase to 0.5 mg, 1.0 mg, 1.7 mg and 2.4mg (maximum dosage) at four weekly intervals. Compounded Semaglutide dosages vary.

Mode of Action: Semaglutide, a GLP-1 agonist, activates GLP-1 receptors in the pancreas, resulting in reduced appetite and delayed glucose absorption, leading to weight loss.


Active Ingredient: Liraglutide

Found in: Saxenda

Description: Liraglutide, a GLP-1 receptor agonist akin to Semaglutide, requires daily injections. Saxenda is the branded version for obesity, while Victoza, which contains the same active ingredient, is marketed for diabetes.

Dosage: Patients start with a daily dose of 0.6 mg, increasing by 0.6 mg weekly until reaching 3 mg, maintaining this dose thereafter.


Active Ingredient: Tirzepatide

Found in: Mounjaro

Description: Mounjaro, a dual agonist for GLP and GIP, gained MHRA approval in 2023 for weight loss and weight management.

Dosage: Patients begin with a weekly injection of 2.5 mg, gradually increasing to a maximum of 15 mg every four weeks in 2.5mg increments.

Mode of Action: As a dual agonist, tirzepatide tends to be more effective than Semaglutide, as evidenced by clinical trials.


Active Ingredient: Retatrutide

Found in: Still in clinical trials; no MHRA approval or brand name released.

Description: Retatrutide, a triple agonist acting on GLP-1, GIP, and glucagon receptors, has shown promise in trials, surpassing tirzepatide and Semaglutide in weight loss.

Mode of Action: Trials demonstrated weight loss of 17.5% at 24 weeks and 24.2% at 48 weeks, making it a potential breakthrough.


Active Ingredient: Naltrexone and Bupropion

Found in: Marketed under the brand name Contrave (or Mysimba in some regions).

Description: Naltrexone and Bupropion is a combination medication used for weight management in adults with a BMI of 30 or greater (obese), or 27 or greater (overweight) in the presence of at least one weight-related comorbidity. It combines the addiction-fighting properties of Naltrexone with the appetite-suppressing effects of Bupropion.

Mode of Action: Naltrexone is believed to inhibit the effects of endogenous opioids that may regulate food intake, while Bupropion is thought to act on the central nervous system to increase satiety and decrease appetite. The combination of these two medications works synergistically to control appetite and cravings, contributing to weight loss.


Choosing a Weight-Loss Drug

The decision between Semaglutide, retatrutide, tirzepatide, liraglutide and Mysimba depends on various factors, including cost, potential side effects, and individual patient preferences.

All these medications have potential side effects, including nausea, constipation, and vomiting, with rare but serious effects like pancreatitis and gallbladder disease.

While trials compare all these drugs, practitioners observe varying responses among patients, with some responding better to one drug over another e.g. responding better to Mounjaro after Wegovy plateauing.

Suitability and Usage while staying on-label is recommended. Some medicines can be prescribed off-label based on individual patient’s circumstances and previous experiences.

These medicines are not limited to weight loss and diabetes; ongoing studies explore their impact on addiction, depression, mental health, and chronic inflammatory illnesses.

In summary, the choice of a weight-loss medication involves a nuanced decision-making process considering individual circumstances, preferences, and medical conditions. To find out which medication you are eligible for, please complete our consultation which is reviewed by our licensed team of clinicians.

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Did you know?

Over 40% of the population has tried to lose weight at some point in the last 5 years – so you’re certainly not alone