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Belviq, or lorcaserin, is a weight-loss drug approved to treat obesity. Its distributor, Eisai Inc., pulled it off the market in the United States in 2020 at the request of the U.S. Food and Drug Administration. The FDA cited increased rates of lung, pancreatic and colorectal cancer among Belviq users during a five-year study of the drug’s risk.

Last Modified: September 5, 2023
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Belviq hit the market in 2012 offering weight-loss hope to people who struggled with obesity. It was also sometimes used to treat overweight people who also had a serious medical condition, such as high blood pressure, high cholesterol or diabetes.

It was the first weight-loss drug approved by the FDA in 13 years. Unlike over-the-counter diet pills or appetite suppressants which are often intended for cosmetic weight loss, Belviq was a prescription drug used to treat obesity.

Obesity and being overweight are two different things. Being overweight simply means weighing too much. Obesity means having potentially dangerous amounts of body fat. Obesity is a chronic condition that can increase a person’s risk for serious health problems including heart disease, diabetes and certain types of cancer.

One 2022 research report noted that preliminary uncontrolled studies of Belviq in patients with Dravet syndrome, a rare form of epilepsy, have yielded promising results.

How Does Belviq Work?

Belviq (pronounced bell-VEEK) works by controlling appetite. The drug activates serotonin receptors in the brain. Serotonin is a neurotransmitter that triggers feelings of well-being such as satisfaction, gratification and being fully fed.

Antidepressants called SSRIs target some serotonin receptors that play a role in a patient’s mood. Belviq only targets the ones that affect appetite.

People take regular versions of Belviq tablets twice a day. Extended-release tablets are taken only once per day. A person on Belviq is supposed to lose five percent of his or her weight during the first 12 weeks of taking the drug when coupled with a low-calorie diet. If this amount of weight loss is not achieved, Belviq treatment should be stopped.

Common Side Effects and FDA Cancer Warning

According to the drug’s label, people in clinical trials with and without diabetes experienced a handful of common side effects. These occurred with more frequency in people taking Belviq than those who took a placebo. Most of the side effects were mild.

Serious side effects included mental changes, cognitive impairment, psychiatric disorders and priapism (an erection lasting more than four hours).

Common side effects include:
  • Headache
  • Dizziness
  • Fatigue
  • Nausea
  • Dry Mouth
  • Constipation
  • Hypoglycemia (in people with diabetes)
  • Back pain (in people with diabetes)
  • Cough (in people with diabetes)

FDA Cancer Warning

On Feb. 13, 2020, the FDA requested that Belviq’s manufacturer, Eisai Inc., voluntarily withdraw the drug over a potential cancer link. The agency based its decision on results from a five-year study of Belviq users called the Cardiovascular and Metabolic Effects of Lorcaserin in Overweight and Obese Patients – Thrombolysis in Myocardial Infarction 61 (CAMELLIA-TIMI 61) clinical trial.

While the FDA found an overall increased occurrence of cancer in people who took Belviq, the agency saw the most increase in the occurrence of three cancer types: pancreatic, colorectal and lung.

Lawsuit Information
Lawsuits against Eisai Inc. claim Belviq led people to develop cancer and the company failed to warn about the cancer risk.
View Lawsuits

What People Who Took Belviq Should Do

The FDA recommended that people stop taking Belviq and talk to their doctors or other health care professionals about alternatives. It also advised that doctors stop prescribing and dispensing the drug. And it recommended that doctors contact patients taking Belviq and warn them about the cancer risk.

The agency did not recommend any special cancer screening for people on Belviq.

The FDA advised people to safely dispose of any unused Belviq at a neighborhood drug takeback location. It also provided instructions on safe disposal if there is no nearby takeback center.

How to safely dispose of unused Belviq
  1. Do not crush Belviq pills — instead mix them with dirt, cat litter, used coffee grounds or some other unappealing material.
  2. Place the mixture in a sealed container or plastic bag.
  3. Throw the mixture into your home trash can.

People should also remove all personal information on the labels of empty Belviq bottles before throwing them into the trash or recycle bin.

People who developed cancer after taking the drug have filed Belviq lawsuits to cover medical costs, lost wages and other costs associated with cancer.

If you have developed cancer after taking Belviq, or noticed other side effects while taking it, you should also report your problems to the FDA’s MedWatch program. You can report online or download a form to mail in. You can also request a form at 1-800-332-1088.

Please seek the advice of a medical professional before making health care decisions.