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Belviq Side Effects

The most common Belviq (lorcaserin) side effects include headache, dizziness and nausea. People with diabetes also commonly suffered hypoglycemia, back pain and cough. As of February 2020, Belviq was withdrawn from the market because of a potential increase in the risk of cancer.

Last Modified: April 27, 2021
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Most reports of side effects with Belviq are minor. These side effects may go away once the body gets used to the medication. If they don’t go away or are bothersome, patients should inform their health care providers.

While most side effects appear to be mild, in January 2020, the FDA released a safety communication warning about the potential increase in cancer risk.

Then on Feb. 13, 2020, the agency said the risk of cancer does not outweigh the weight loss benefits of the drug and the agency requested that Eisai Inc. — Belviq’s manufacturer — withdraw the drug from the U.S. market.

Belviq and Belviq XR are no longer available in the United States.

Common Side Effects of Belviq

A search in the FDA Adverse Events Reporting System (FAERS) Public Dashboard for lorcaserin, lorcaserin hydrochloride, Belviq and Belviq XR shows that the top three most reported side effects are headache (505), fatigue (446) and dizziness (363).

FAERS shows 3,010 total cases, 437 serious cases and 16 deaths for the period of 2013 to December 31, 2020. The reports of adverse events peaked in 2014 at 1,165 and tapered off by 2020 with 89 adverse events reported.

The FAERS data matches the top side effects reported on Belviq’s prescription information from clinical trials, which are headache, dizziness and fatigue. Researchers considered a side effect common if it occurred more often in people who took Belviq versus placebo and occurred in five percent or more of trial participants.

Side Effects Reported by Greater Than or Equal to Two Percent of Belviq Patients and More Commonly than with Placebo in Patients without Diabetes Mellitus
  • Back pain
  • Constipation
  • Cough
  • Diarrhea
  • Dizziness
  • Dry mouth
  • Fatigue
  • Headache
  • Musculoskeletal pain
  • Nasopharyngitis
  • Nausea
  • Oropharyngeal pain
  • Rash
  • Sinus congestion
  • Upper respiratory tract infection
  • Urinary tract infection
  • Vomiting
Side Effects Reported by Greater Than or Equal to Two Percent of Belviq Patients and More Commonly than with Placebo in Patients with Diabetes Mellitus
  • Anxiety
  • Back pain
  • Cough
  • Depression
  • Dizziness
  • Fatigue
  • Gastroenteritis
  • Headache
  • Hypertension
  • Hypoglycemia
  • Insomnia
  • Muscle spasms
  • Nasopharyngitis
  • Nausea
  • Peripheral edema
  • Seasonal allergy
  • Stress
  • Toothache
  • Urinary tract infection
  • Worsening of diabetes mellitus
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

Serious Side Effects

Because Belviq activates serotonin receptors in the brain, it may cause serious interactions with SSRI antidepressants such as Paxil or Prozac.

Pregnant women should not take Belviq because weight loss provides no benefit to pregnant women. The drug may also harm the fetus. There are not enough studies to determine if the drug can cause birth defects.

Belviq is a Schedule IV substance with the potential for abuse and psychic dependence.

Belviq side effects that require immediate medical attention include:
  • Easy bleeding or bruising
  • Mental or mood changes
  • Confusion
  • Thoughts of suicide
  • Depression
  • Difficulty with memory or concentration
  • Unusual agitation
  • Shaking or twitching muscles
  • Changes in heart rate
  • Unexplained fever
  • Swelling of the hands, feet or ankles
  • Shortness of breath
  • Breast swelling and unusual breast milk discharge
  • Erections lasting 4 hours or more
  • Sensations of standing outside your body

Potential Cancer Risk

According to the FDA’s review of data from the Cardiovascular and Metabolic Effects of Lorcaserin in Overweight and Obese Patients – Thrombolysis in Myocardial Infarction 61 (CAMELLIA-TIMI 61) clinical trial, more patients who took lorcaserin in clinical trials were diagnosed with cancer than those who took placebo.

The agency doesn’t have an estimate of the absolute cancer risk, but it found “462 (7.7 percent) patients treated with lorcaserin were diagnosed with 520 primary cancers compared to the placebo group, in which 423 (7.1 percent) patients were diagnosed with 470 cancers,” according to its Feb. 13, 2020, Safety Communication.

The most common cancers found in the study were pancreatic, colorectal and lung.

After these findings were made public, several people who were diagnosed with cancer after taking Belviq filed lawsuits against Eisai Inc. The lawsuits say the drug led people to develop cancer and the company failed to warn about the cancer risk.

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