Tirzepatide, also known as Zepbound, is a medication that is approved by the FDA for weight loss in people who are obese (with a body mass index (BMI) over 30 kg/m2) or overweight (BMI over 27 kg/m2) with medical conditions such as diabetes or heart disease. It is meant to be used in combination with diet and exercise. It is important to note that this medication is not approved for people who are only a few pounds overweight. Tirzepatide is given as a once weekly injection.
Tirzepatide belongs to a class of medications called GLP-1 agonists, which were originally developed to treat type 2 diabetes. Glucagon like-peptide (GLP)-1 is a hormone that is produced by the body when we consume food. GLP-1 increases insulin release and slows stomach emptying, which can make you feel full and decrease your appetite. It may have other effects in the body that we don’t completely understand yet. GLP-1 produced naturally is rapidly broken down by the body. GLP-1 agonist medications like tirzepatide work by providing higher concentrations of GLP-1 for longer periods of time, which is thought to increase weight loss. In addition, tirzepatide also works as an agonist of another similar hormone in the body glucose-dependent insulinotropic polypeptide (GIP), which may provide additional benefit over other GLP-1 medications.
Ozempic, Mounjaro, and Wegovy are all GLP-1 agonists. The dosing between medications may be a little different, but they all work in the same way. Ozempic and Mounjaro are approved by the FDA to treat high blood sugar in people with type 2 diabetes. Wegovy and tirzepatide are approved for weight loss in people who do not have diabetes. While tirzepatide is a GLP-1 agonist, it also works on GIP, which may make it more effective, but studies are limited at this time.
In one study, the average weight loss for patients taking tirzepatide was 52 pounds. While this sounds very promising, it is also important to remember that these results occurred in patients enrolled in a study where they were closely monitored. The results may not be the same with real-world use, and individual results may vary. In addition, individual diet and exercise patterns can impact weight loss. Because these drugs are relatively new, we also do not know how long the weight stays off and how long people should be on the medication.
Tirzepatide mostly causes gastrointestinal side effects, including nausea, vomiting, and bloating. In severe cases, the stomach can stop emptying (gastroparesis), which can be serious. While information is limited, tirzepatide and other GLP-1 agonists have been reported to cause suicidal thoughts, inflammation of the pancreas, low blood sugar, and gall bladder problems. Allergic reactions, including anaphylaxis have been reported.
There are some people that should not take tirzepatide. People who have a personal or family history of thyroid and endocrine tumors should not take GLP-1 agonists. Also people who already have problems with stomach emptying should talk to their doctor before taking tirzepatide.
Because tirzepatide and other GLP-1 agonists alter stomach emptying, they can affect the absorption of other medications. One important type of medication is birth control pills. GLP-1 agonists can decrease absorption of birth control pills, which may lead to unplanned pregnancy. People should consider alternative forms of birth control while taking medications like tirzepatide. Because absorption of other medications can also be affected, you should talk to your doctor about the medications you are taking and you may need to be monitored after starting tirzepatide.
If you think you or someone else took too much tirzepatide or is having a reaction to tirzepatide, immediately contact the poison center at 1-800-222-1222 for further guidance. Expert and free case-specific guidance is also available online, 24/7, www.poison.org.
Maryann Amirshahi, PharmD, MD, MPH, PhD
Medical Toxicologist
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