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Federal regulators are alerting the public that the prescription weight-loss drug Belviq may be associated with an increased risk of cancer, though it's unclear how big of a risk that might be.

The Food and Drug Administration published the alert Tuesday afternoon, saying that a clinical trial assessing the medication's safety showed a "possible increased risk of cancer." Belviq is also known in its generic form as lorcaserin.

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"The cause of the cancer is uncertain, and we cannot conclude that lorcaserin contributes to the cancer risk," the alert said. "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 alert about Belviq includes both the tablet form and the extended release version of the pill (Belviq XR). Eisai via AP

The FDA approved Belviq in 2012 as a prescription drug to help overweight and obese adults lose weight. It works by making people feel full.

The study that raised FDA concerns comes from the drug's manufacturer, Eisai. The company study tracked about 12,000 participants who took either the medication or a placebo over a five-year period.

"More patients taking lorcaserin were diagnosed with cancer compared to patients taking placebo, which is 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 alert said.

It's unclear what type or types of cancer were diagnosed.

The FDA suggests that patients on lorcaserin speak with their doctors about whether the benefits of taking the weight management pill outweigh any potential risks.

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