Hopes for new pill to combat obesity took a hit Thursday when a Food and Drug Administration (FDA) advisory panel voted 10 to six to recommend against approving the drug Qnexa as a prescription weight control aid.

Those voting against the drug, developed by Vivus, cited potential side effects, such as increased heart rate, birth defects, and psychiatric problems. Those voting in favor of the drug said obesity itself was a greater health risk.

The recommendation goes to the FDA, which may or may not follow it. The agency will make a decision in October and, because of the split vote, the decision is harder to predict.

"No one wants to conduct a large public health experiment on the population," said Dr. Elaine Morrato, a panel member from the University of Colorado, Denver.

Obesity drug obstacles

Drug companies have placed new emphasis on developing medications to promote weight control, as obesity has become a greater public health concern. The track record is not inspiring.

The last major weight control drug disaster was fen-phen, which was withdrawn from the market in 1997 after it was shown to cause heart valve damage. Qnexa includes phentermine, part of the phen-fen cocktail that was allowed to stay on the market. The drug company said people taking Qnexa in clinical trials reported success in losing weight.

The company said it is holding out hope the FDA will approve Qnexa in spite of the advisory panel's vote. CEO Leland Wilson held a conference call with reporters following the vote and said the company will not give up on the drug.

"The advisory committee vote is a recommendation, not a final step," he said.