The US Food and Drug Administration warns that prescription weight loss medicine Belviq might be associated with an increased risk of cancer.

The findings were the result of a clinical trial assessing the safety of the drugs Belviq and Belviq RX, or lorcaserin, the FDA announced on Tuesday.

"At this time, the cause of the cancer is uncertain, and we cannot conclude that lorcaserin contributes to the cancer risk. However, we wanted to make the public aware of this potential risk. We are continuing to evaluate the clinical trial results and will communicate our final conclusions and recommendations when we have completed our review," the FDA said in its announcement.

The agency went on to note that health care professionals should consider if the benefits of taking lorcaserin exceed the potential risks for a patient, and that patients currently taking the drug should talk to their doctors about the potential increased risk of cancer.

The drug manufacturer, Eisai Inc., responded to the FDA's announcement in a written statement on Wednesday.

"Patient safety is Eisai's priority and we will continue to work closely with the FDA to evaluate the clinical trial results," the statement said. "We recommend patients speak directly with their health care professional in order to make the best decision about their medical treatment. As indicated in the FDA's communication, at this time, the FDA and Eisai cannot conclude that BELVIQ increases the risk of cancer."

Lorcaserin, an oral medication, was approved by the FDA in 2012 and made available by prescription the year following to help weight loss in adults who are obese or are overweight and have weight-related medical problems, according to the FDA.

Lorcaserin -- available as Belviq, which is a twice-daily tablet, and Belviq XR, which is an extended-release once-daily tablet -- works by increasing feelings of fullness so that you eat less food.

The FDA said in its announcement that, when approving lorcaserin, the agency required the drug manufacturer, Eisai Inc., to conduct a randomized, double-blind, placebo-controlled clinical trial to evaluate the risk of heart-related problems. In the trial, conducted in about 12,000 participants over five years, more patients taking lorcaserin were diagnosed with cancer compared to patients taking a placebo, which was an inactive treatment.

"Our evaluation of this potential signal is ongoing, and at this time it is uncertain if lorcaserin increases the risk of cancer," the FDA said.

Weight loss drugs approved for long-term use include orlistat (brand name Xenical), lorcaserin (Belviq) and liraglutide (Saxenda) as well as the combination drugs naltrexone-bupropion (Contrave) and phentermine-topiramate (Qsymia).

In one recent study, these drugs helped overweight or obese people lose at least 5% of their body weight at the end of a year -- that's at least 10 pounds if you weigh 200 -- compared with a placebo. Qsymia and Saxenda were associated with the highest odds of achieving that amount of weight loss.

For many, losing 5% to 10% of your body weight is associated with improved blood pressure, triglycerides and blood sugar, factors that lower the risk for heart disease and diabetes.

CNN's Lisa Drayer contributed to this report.

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