The Food and Drug Administration continues to have concerns that a weight-loss drug it is reviewing for the second time can cause birth defects and heart problems, documents released by the agency on Friday show.

The drug, called Qnexa, was rejected by the agency in 2010, largely because of those risks. A committee of outside advisers to the F.D.A. will meet on Wednesday to consider again whether the drug, developed by Vivus, should be approved.

Some obesity specialists and patient advocates say there is a strong need for new obesity drugs to help bridge a treatment gap between diet and exercise, which do not work for many people, and the more radical option of bariatric surgery. But the F.D.A. has been cautious, in part because with two-thirds of American adults overweight or obese, such drugs might be used for a long time by millions of people.

Qnexa is a combination of two existing drugs: the stimulant phentermine and the epilepsy and migraine drug topiramate, also known by the brand name Topamax. Some doctors say they believe the component drugs are an effective tool to combat obesity and prescribe the two component drugs to patients off label, which is legal.