The pros and cons of the new GLP-1 weight loss/diabetes drugs, like Ozempic and Mounjaro

By Brooke Hudspeth
University of Kentucky

Most people have likely heard about the new weight-loss and diabetes management drugs called Ozempic and Mounjaro, which are also called GLP-1 medications, short for glucagon-like peptide-1 agonists, but they may not have heard about their side effects.

While those more commonly known brands of these medications are relatively new, GLP-1 analogs have been around for 20 years. In 2005, the U.S. Food and Drug Administration approved the first-ever GLP-1 agonist, exenatide (Byetta). Since then, several others have followed, including dulaglutide (Trulicity), liraglutide (Victoza, Saxenda), semaglutide (Ozempic, Wegovy), and the latest FDA-approved medication, tirzepatide (Mounjaro, Zepbound).

With the semaglutide and tirzepatide versions of these drugs gaining the most media attention and curiosity in recent years due to their high effectiveness, this health column will focus on these two medications.

What do these medications do?

GLP-1 is a hormone that occurs naturally in the body and is created by the small intestine. It serves several functions, including:

• Triggering the pancreas to release insulin, which lowers blood sugar
• Suppressing glucagon, a hormone that raises blood sugar
• Slowing down digestion
• Increasing feelings of fullness after eating

GLP-1 medications mimic this natural hormone by binding to GLP-1 receptors in the body, and are intended to be used alongside a healthy diet and exercise. By helping to regulate blood sugar, these medications support the management of Type 2 diabetes.  Other effects of these medications often lead to weight loss.

What’s the difference between these two drugs?

Ozempic is the name-brand version of weekly injectable semaglutide that is FDA-approved for diabetes treatment, while Wegovy is the same injectable approved for obesity treatment. A daily oral (pill) version of semaglutide, Rybelsus, was approved for type 2 diabetes treatment in 2019.

Mounjaro is the name brand of tirzepatide approved for diabetes treatment. Meanwhile, Zepbound is the same drug formulation for the treatment of both obesity and/or obstructive sleep apnea. Tirzepatide is taken in a once-weekly injection. Additionally, tirzepatide mimics two hormones produced in the body – in addition to being a GLP-1 agonist, it also activates the glucose-dependent insulinotropic polypeptide (GIP) hormone receptors.

A recent New England Journal of Medicine study showed that while both these new drugs are highly effective, tirzepatide was shown to be more effective for weight loss, possibly because of the combination of these two hormone agonists, compared to the single hormone agonist in semaglutide.

What are the side effects of these drugs?

While GLP-1 agonists have many positive benefits, they do have a number of potential side effects.

The most common side effects include:

• Gastrointestinal issues, like constipation, diarrhea, nausea and vomiting, due to the drugs’ effect on digestion
• Cosmetic changes, including hair loss, muscle loss, loose or sagging skin, and more pronounced wrinkles (The term “Ozempic face” has been used to describe these changes, but the effects are due to rapid weight loss, not the medications themselves.)
• Increased heart rate:  Several GLP-1s are beneficial to heart health, but some patients report a slightly elevated heart rate while on them.
• Injection site reactions

Though not common, some side effects of these medications can be severe. These include:

• Gallstones and gallbladder issues, thought to be caused by rapid weight loss
• Pancreatitis — studies have shown a higher risk for this condition while taking GLP-1 medications compared to other weight loss medications
• Gastroparesis (delayed stomach emptying) — though these medications are designed to slow down digestion, if it slows down too much, it can lead to other symptoms and complications
• Kidney damage, typically resulting from dehydration caused by other side effects
• A potential risk of thyroid cancer — animal studies have shown an increased risk for thyroid C-cell tumors, though that risk has not yet been confirmed in humans

GLP-1 medications can be a powerful tool for people to improve their health, but they’re not for everyone. They require a prescription, and it’s important to speak with a trusted health care provider to discuss your personal goals, medical history and health risks before taking them.

This week’s health column is by the UK College of Pharmacy’s Brooke Hudspeth, Pharm.D., chief practice officer.