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En español | The recall of a pair of weight loss drugs could have consumers worried about cancer, but experts say those risks appear to be small.
The Food and Drug Administration (FDA) this month requested that the makers of Belviq and Belviq XR voluntarily withdraw the products from U.S. shelves after finding evidence they raised the risk of lung, colon and pancreatic cancers.
"I don't think people should be worried. Belviq was pulled off as a precaution,” says Dan Azagury, chief of bariatric surgery at Stanford Health Care, who notes that other recalled weight loss drugs, such as fen-phen in 1997, had much more evident links to very serious complications. Anyone who has a prescription for Belviq, however, should stop taking the drug immediately, doctors say.
The FDA says the cancer link was less than certain, and cancer has not been a cause of concern with weight loss drugs in the past, experts say. Pulling the drug from shelves may be possible partly because recalls of weight loss drugs face relatively little resistance.
“It is far easier and more tolerable to pull drugs off the market to treat obesity than cancer,” at least in part because they don't show dramatic results and don't make a lot of money, says Lee M. Kaplan, director of the Obesity, Metabolism and Nutrition Institute at Massachusetts General Hospital in Boston.
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Previous weight loss drugs have been pulled from the market for causing cardiac problems related to how they speed up metabolism or increase heart rate. Some have also caused problems with heart valves.
Diet drugs you can still take — and how they work
The recall of Belviq leaves four weight management drugs approved by the FDA: Qsymia (phentermine/topiramate), Contrave (bupropion/naltrexone), Saxenda (liraglutide) and orlistat (Xenical).
Healthy diets and exercise are always recommended ahead of any prescription, but experts say these drugs can be important tools in the battle against obesity, which affects 40 percent of American adults. Drugs can be recommended for those with a body mass index, or BMI, of 30 or higher, or one of 27 or higher if it's accompanied by health problems such as high blood pressure or Type 2 diabetes.
If most patients can expect to lose between 5 and 10 percent of their weight with the proper diet and exercise, the FDA-approved diet drugs can add another 5 to 7 percent loss, says Scott Lynch, medical director of the bariatric center at the Mayo Clinic in Jacksonville, Florida.
The drugs are not, however, one size fits all. Not only do they work differently in the body, but some are used long term and others can be used only short term. Sometimes, Kaplan says, “patients need to be tried on different drugs” before finding the right fit.
If you took Belviq
In its public comments recommending a voluntary recall of Belviq, the FDA stated that “the cause of the cancer is uncertain and we cannot conclude that [Belviq] contributes to the cancer risk.”
The FDA does not recommend that patients who have taken the drug get special cancer screening.
Studies conducted since Belviq was approved for use in 2012 found that of 1,200 patients taking it, about 7.7 percent were diagnosed with cancers, compared to 7.1 percent in a placebo group.
Eisai, which manufactured the two formulations of Belviq, complied with the FDA's request to remove the products from the market but noted that the drugs continue to have “a positive benefit-risk profile in the patient population for which they are indicated."
Better diet drugs to come?
As scientists learn more about weight regulation, pharmaceutical companies are working to develop safer medications that target hormones and chemical messengers in the body called neurotransmitters, instead of metabolic pathways that can stress or damage the heart. “Our understanding of weight loss management is still in development, but it's no longer just about calories in and out and willpower,” Lynch says.