Liraglutide vs semaglutide: how Victoza and Saxenda compare

Fourteen years ago, liraglutide - an older relative of semaglutide (Ozempic and Wegovy) - became available.

Liraglutide is marketed under the brand names Victoza and Saxenda.

The patents covering Victoza and Saxenda have now expired, prompting other pharmaceutical companies to develop "generic" alternatives. These versions are likely to cost only a fraction of the current price, which is about A$400 per month.

So, how does liraglutide measure up against semaglutide?

How do these drugs work?

Liraglutide was initially created to treat type 2 diabetes rather than as a treatment for weight loss. Semaglutide (Ozempic) was also first used for type 2 diabetes.

Both liraglutide and semaglutide are part of a group of medicines called GLP-1 mimetics, which imitate the naturally occurring hormone GLP-1. Your small intestine releases this hormone after you eat, and it improves how your body processes glucose (sugar) in several ways.

How do liraglutide and semaglutide reduce hunger?

Liraglutide works in several areas of the unconscious brain, including the hypothalamus, which regulates metabolism, and regions of the brain stem that relay information about your body's nutritional state to the hypothalamus.

Its effects in these areas seem to curb hunger through two separate mechanisms. Firstly, it helps you feel full sooner, so smaller portions are more satisfying. Secondly, it changes your "motivational salience" for food, reducing the quantity of food you look for.

The original version of liraglutide, developed for type 2 diabetes, was sold as Victoza. Its capacity to produce weight loss became apparent not long after it was introduced.

A higher-strength version, Saxenda, was subsequently launched for weight loss in people with obesity.

How much weight can you lose with liraglutide?

Responses vary between individuals, so the amount of weight lost will differ. The figures below represent the average weight loss users might expect: some people lose more, occasionally much more, while others lose less and a small number do not respond.

Exenatide (Bayetta) was the first GLP-1 mimicking drug. While it remains available for treating type 2 diabetes, no generic versions are currently available. Exenatide can result in weight loss, although this is relatively modest, usually about 3–5 percent of body weight.

People using liraglutide for obesity take the stronger Saxenda formulation, which generally produces weight loss of around 10 percent.

The stronger semaglutide formulation, Wegovy, generally leads to 15 percent weight loss.

The latest GLP-1 mimicking drug available, tirzepatide - sold as Mounjaro for type 2 diabetes and Zepbound for weight loss - results in weight loss of approximately 25 percent of body weight.

What happens when you stop taking them?

Although these medicines can be effective for weight loss, they do not seem to alter a person's weight set-point.

As a result, many people who stop using them regain weight towards their starting weight.

What is the dose and how often do you need to take it?

Liraglutide prescribed as Victoza for type 2 diabetes is precisely the same medicine as Saxenda for weight loss, although Saxenda is given at a higher dose.

While both formulations act on the same target, the GLP-1 receptor, liraglutide used to control glucose in type 2 diabetes needs to reach the pancreas, primarily.

For weight loss, however, it must reach areas of the brain. This requires it to cross the blood–brain barrier, and because not all of the drug gets through, a larger dose is required.

Every currently available GLP-1 mimicking drug formulation is injectable. The arrival of generic liraglutide will not alter this.

They do, however, differ in injection frequency. Liraglutide is injected once a day, while semaglutide and tirzepatide are injected once a week. (This makes semaglutide and tirzepatide considerably more appealing, although generic semaglutide will not be available until 2033.)

What are the side effects?

As all of these medicines act on the same bodily target, their side effects are largely similar.

The most frequent effects are gastrointestinal problems, including nausea, vomiting, bloating, constipation and diarrhoea. These occur partly because the medicines slow the rate at which food leaves the stomach, but they can generally be managed by raising the dose gradually.

Recent clinical data indicates that delayed stomach emptying may cause problems for some people and could raise the risk of food entering the lungs during an operation. It is therefore important to tell your doctor if you are taking any of these medicines.

Because they are injected, these medicines may also cause reactions at the injection site.

Some cases of thyroid disease and pancreatitis, or inflammation of the pancreas, were reported during clinical trials. However, it is unclear whether GLP-1 mimicking drugs were responsible.

In animals, GLP-1 mimicking drugs have been found to adversely affect embryo growth. There is currently no controlled clinical trial evidence about their use during pregnancy, but the animal findings mean these medicines should not be used during pregnancy.

Who can use them?

GLP-1 mimicking medicines for weight loss - Wegovy, Saxenda and Zepbound/Mounjaro - are approved for people with obesity and are intended to be used only alongside diet and exercise.

A doctor must prescribe these medicines. They are not covered by the Pharmaceutical Benefits Scheme for obesity, which is one reason they are costly. In time, though, generic liraglutide versions are likely to become more affordable.

Sebastian Furness, ARC Future Fellow, School of Biomedical Sciences, The University of Queensland

This article is republished from The Conversation under a Creative Commons licence. Read the original article.