In February, the manufacturer of the weight-loss medication lorcaserin (Belviq, Belviq XR) voluntarily withdrew the drug from the US market at the request of the FDA. This was a result of emerging data showing that people who had taken the drug as part of a large clinical trial had an increased occurrence of cancer five years later.

What were the findings about Belviq, and why did this information come to light now?

Lorcaserin was approved by the FDA in 2012. As part of the approval process, the FDA reviewed a series of clinical trials that looked at its effects on weight and its safety profile, compared to a placebo.

Based on these studies, the drug was approved, but a larger study to assess its cardiovascular safety was mandated by the FDA. In that subsequent study, published in the New England Journal of Medicine, 12,000 people with overweight or obesity and cardiovascular disease (CVD) or risk factors for CVD took either lorcaserin or a placebo. During the three-year follow-up, as published in 2018, those who took lorcaserin had more weight loss and comparable rates of cardiovascular events compared to those who took a placebo. So from a cardiovascular safety perspective, the study was reassuring.

But the study subjects continued to be followed, and what recently came to light is that at five years, the group that took the drug has had a slight increase in the occurrence of cancers compared to those who took a placebo (7.7% of lorcaserin subjects developed cancer, compared to 7.1% in the placebo group). Increases in several different types of cancers were observed, including pancreatic, colorectal, and lung.

Where does the recall leave people who are currently taking Belviq?

Based on the evidence we have now, it is still uncertain whether lorcaserin truly increases the risk of cancer. And we don’t know anything about the mechanisms of how this drug could have such effects. It is also critical to reiterate that this possible increase in cancer occurrence is very small; 7.1% of people developed cancer if they were taking placebo, and 7.7% if they were taking lorcaserin.

That said, people taking lorcaserin are advised to stop taking it and contact the doctor who prescribed it for guidance on next steps. The FDA is not recommending any special cancer screening or other testing at this time.

Could my doctor prescribe a different weight-loss medication?

Loracaserin is one of several medications currently FDA-approved for weight loss in people who have overweight with weight-related medical issues, or who have obesity. For those who have not had success losing weight through diet, exercise, and other healthy lifestyle changes, or for people who have been unable to sustain the weight loss they do achieve, weight-loss medications can play an important role. By changing the biology of the systems that regulate weight, and suppressing appetite and cravings, medications can help people lose weight even if other strategies have not worked. Lorcaserin, for example, works by affecting brain serotonin signaling, making you feel more full, so you eat less.

However, since each medication works in a unique way, someone who experienced weight loss with lorcaserin is not necessarily going to experience a similar effect from another medication. You may need to work with your doctor to try different options to find one that is effective.

Do the new findings mean all weight-loss medications are unsafe?

These new findings do not in any way reflect the safety of other weight-loss medications on the market. Weight-loss medications have a storied history with safety recalls, and lorcaserin is not the first weight-loss medication to get pulled off the market after many years of patient use — fenfluramine/phentermine (Fen-Phen) and sibutrimine (Meridia) are other examples.

Still, it is unsettling to learn that a widely used, FDA-approved medication demonstrates serious safety concerns. On the other hand, it is important to underscore that, as in the case of lorcaserin, the FDA evaluates safety outcomes, and continues to rigorously monitor products on the market. This is in contrast to weight-loss supplements, which are not regulated by the FDA. Americans spend millions of dollars every year on these unregulated weight-loss products, which tout incredible results with no credible studies and no ongoing safety monitoring, and which can have serious adverse health consequences.

Anyone considering weight-loss medications or products should work with licensed health care professionals. The experience with lorcaserin is a good reminder to use only interventions that have scientific studies that evaluate safety as well as benefits. And it is comforting that close monitoring and regulatory processes are in place to ensure our safety.

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