In recent years, weight loss drugs have gained traction as a popular method for rapidly losing weight, though they remain controversial.

This controversy partly stems from the side effects associated with well-known medications like Ozempic and Mounjaro. The Obesity Medicine Association states that researchers continue to study these drugs’ side effects.

Here are some side effects of the eight FDA-approved weight loss drugs:

Ozempic and Wegovy

Semaglutide, sold under the brand names Ozempic and Wegovy, is a drug that, according to Harvard Health, has been used for around 20 years to treat Type 2 diabetes. Ozempic has sparked debate recently as more individuals with weight issues have sought it for weight loss, leading to a shortage for those needing it for diabetes management.

Wegovy is the brand name for a form of semaglutide that has since been approved for weight loss.

Semaglutide, which mimics a natural hormone called GLP-1, helps regulate blood sugar while slowing down the emptying of the stomach and signaling satiety or fullness to the brain.

The OMA reports that the most common complaint among patients using semaglutide is gastrointestinal issues like nausea. Other side effects include fatigue, dizziness, headache, bloating, belching and heartburn.

An American Medical Association study has also found that  GLP-1 agonists are associated with an increased risk of pancreatitis, bowel obstruction, and gastroparesis.

While headlines have warned about an increase in suicidal ideation with semaglutide, a January 2024 study in Nature Medicine suggested “a 49% to 73% lower risk of first-time or recurring suicidal ideations” compared with other obesity medications.

Mounjaro and Zepbound

Mounjaro and Zepbound are drugs known as tirzepatide. Mounjaro was approved in 2017 to treat Type 2 diabetes, while Zepbound was approved in more recent years to treat obesity.

Like semaglutide, tirzepatide is a GLP-1 agonist that increases a person’s feeling of fullness and helps them maintain a weight loss diet.

It causes common mild symptoms like nausea, constipation, diarrhea and bloating, but the OMA reports more serious side effects like kidney problems up to and including kidney failure, gallbladder symptoms, pancreatitis and hypoglycemia.

Manufacturer Eli Lilly warns, however, that Tirzepatide may cause thyroid tumors or thyroid cancer. Patients should monitor themselves for symptoms like neck swelling, hoarseness, problems swallowing and shortness of breath.

Contrave

Contrave is the brand name for a medication that combines two drugs, bupropion and naltrexone. Bupropion, which is marketed under the brand name Wellbutrin, is an antidepressant that is also known to reduce a person’s appetite.

Naltrexone, commonly sold under the brand names Revia and Vivitrol, is a medication used to treat drug and alcohol addiction. According to Drugs.com, naltrexone works by blocking the euphoric, intoxicated feeling of alcohol and opioids. It also helps reduce the cravings for the substances.

The OMA reports that patients should not be prescribed Contrave if they suffer from a seizure disorder or if they take opioids for chronic pain.

The most common side effects of the drug are nausea, vomiting, constipation, diarrhea, headache, dizziness, dry mouth and insomnia.

Saxenda

Saxenda is a medication containing liraglutide, a drug that mimics a person’s natural hormones affecting hunger, digestion and feelings of fullness. It was approved by the FDA in 2017 to treat obesity in people 12 and older.

The most common side effects of liraglutide are nausea, vomiting, constipation, diarrhea, headache, fatigue, dyspepsia, dizziness and abdominal pain.

It can also cause increased heart rate, increased lipase, which is a pancreatic enzyme, and decreased kidney function.

Qsymia

Qsymia is a medication that combines the drugs phentermine and topiramate. According to the OMA, phentermine has been around since 1959, making it the oldest and most widely used weight loss medication.

The drug, which works in the brain as an appetite suppressant, is a stimulant similar to amphetamines and can be abused. It should not be used by patients who have suffered a stroke or who have heart disease, glaucoma or hyperthyroidism.

The side effects of phentermine can be serious, including fast or irregular heart rate, headache, overstimulation, high blood pressure and tremors. It can also interact with several other drugs, including MAO inhibitors, alcohol, adrenergic neuron blockers and some anesthetic agents.

When phentermine is combined with topiramate, an anticonvulsant, its effect on hunger is magnified.

The side effects of the two drugs combined include dizziness, abnormal sensations, altered taste, insomnia, constipation and dry mouth. Topiramate also carries a risk of birth defects, so it should not be taken during pregnancy.

Qsymia was approved in 2021 for chronic weight management in adults. It was approved the following year for pediatric patients ages 12 and older who have a body mass index in the 95th percentile or greater.

Imcivree

Imcivree, which is the brand name for setmelanotide, is approved by the FDA to treat patients suffering from severe obesity caused by rare genetic disorders. According to the National Institute of Health, setmelanotide is used to treat POMC, PCSK1 and LEPR deficiencies, which all lead to early-onset obesity.

According to manufacturer Rhythm Pharmaceuticals, it is also used to treat Bardet-Biedl syndrome in patients aged 2 and older.

Setmelanotide works by targeting the impaired MC4R pathway in the brain, which allows it to deliver messages to the brain that the body is satisfied and doesn’t need more food. The National Institute of Health reports that it helps restore appetite control, reduces the patient’s food intake and helps to control weight gain.

It does not treat the underlying genetic defects that lead to obesity.

The most common side effects of Imcivree are reactions at the injection site, hyperpigmentation, nausea, vomiting, headache, diarrhea, stomach pain and depression. More serious side effects include sexual dysfunction, depression, suicidal thoughts or actions and toxicity caused by benzyl alcohol, which is a preservative in Imcivree.

Like most medications, it can also cause serious allergic reactions that include swelling of the face, lips, tongue or throat, breathing or swallowing issues, severe rash, itching, dizziness and rapid heartbeat. Anyone who experiences an allergic reaction should seek immediate medical attention.

NewsNation’s Taylor Delandro contributed to this report.