Dec. 24, 2014 -- A drug that treats type 2 diabetes has gotten FDA approval for another use: weight loss.
Saxenda is the fourth drug for weight loss OK'd by the agency since 2012. It's already available in a lower dose as Victoza for type 2 diabetes.
Researchers began to study it as an obesity treatment after people on Victoza reported weight loss.
WebMD asked two experts to address commonly asked questions about Saxenda.
How does the drug work to achieve weight loss?
It mimics a hormone made in the intestines called GLP-1 (glucagon-like peptide), says William Troy Donahoo, MD. He's a staff physician in the Metabolic-Surgical Weight Management Department, Kaiser Permanente, Denver.
One role of GLP-1 is to tell your brain you’re full, he says.
The medicine works in many ways to help beta cells normalize blood sugars. Beta cells make and release insulin when blood sugar is high. They help those with type 2 diabetes keep their blood sugar normal.
How well does Saxenda work?
Donahoo says he expects a range of weight loss responses to Saxenda, just as he has seen various responses from people on Victoza for their diabetes.
"Clinical trials show that [more than] 60% of patients getting a daily 3-milligram injection lost at least 5% of their weight and 31% lost more than 10%," says Osama Hamdy, MD, PhD. He's the medical director of the Obesity Program at Joslin Diabetes Center.
In comparison, 34% of those on placebo lost at least 5% of their body weight, according to the FDA.
"It is not an impressive weight loss for an injectable and expensive medication with a lot of potential side events,” Hamdy says. He also says people generally lose less weight outside of clinical trials.
How does Saxenda compare with other weight loss drugs?
It hasn't been compared directly with other recently approved weight loss drugs, including Belviq, Contrave, and Qsymia. Based on the clinical trial information, Donahoo predicts Saxenda will be ''not quite as good as Qsymia but probably better than Belviq."
For some who prefer to take medications by mouth, the injection may be a barrier, Donahoo says.
Hamdy agrees. "I wonder who will take an injection for weight loss if you have another three effective oral alternatives," he says. "This medication [Saxenda] came too late and in the wrong time and patients may not have enthusiasm for it."
What are the major side effects or downsides?
In clinical trials, some people said they had nausea. "For some, it's intolerable," Donahoo says.
Besides nausea, others have reported vomiting, diarrhea, constipation, low blood sugar, and increased appetite, according to the FDA.
Serious side effects can include pancreatitis, gallbladder disease, kidney problems, and suicidal thoughts. It can also raise heart rate.
The drug will include a boxed warning about thyroid tumors. People with a family history of a specific type of thyroid cancer should not take the drug.
The FDA will continue to look at the risk of thyroid cancer, along with breast cancer, in the drug’s post-marketing studies. It will also judge Saxenda’s safety for children, its effect on sexual function and central nervous system development, and for heart risks.
How long will Saxenda need to be taken for weight loss and control?
Experts say they're not sure how long would be best, since the clinical trials lasted about a year.
The FDA says people should be checked after using it for 16 weeks to see if it's working. If a patient hasn’t lost at least 4% body weight, they should stop the drug.
"I think we need to think about weight loss medications like other drugs, such as cholesterol and high blood pressure medicines,” Donahoo says. “They may be considered for long-term use, perhaps forever."
What about its effect on blood sugar?
"It only has an effect on blood sugar if it's high,'' Donahoo says, or if you're taking other diabetes medicines.
When will Saxenda become available? What will it cost? And will insurance cover it?
Novo Nordisk, which distributes the drug in the U.S., expects Saxenda to be in pharmacies by early 2015, says spokesman Ken Inchausti.
The price is not yet set, he says. Novo Nordisk is talking with several insurance companies about coverage, he says.