Food and Drug Administration staff said in documents posted online that the drug Qnexa did help people lose weight, though they reiterated concerns about the risk of birth defects and heart problems.

The FDA rejected Qnexa in 2010 because of safety problems, and on Friday agency staff still seemed skeptical about the drug's long-term health effects, especially on the heart.

FDA staff will ask a panel of outside experts next Wednesday to consider whether the benefits of Qnexa for obese patients outweigh its safety risks, or if the company needs to do more studies.

Obesity, a leading cause of diabetes, heart disease and other serious health problems, has reached epidemic proportions in the United States, with about a third of the population affected.

But the FDA has set a high approval bar for weight loss drugs because such a large portion of the general population is likely to want to take them. The agency has not approved a new obesity drug since 1999.

Qnexa is one of three obesity pills up for a second round of consideration from the FDA.

"Ultimately, only a long-term, cardiovascular outcome trial can define the effect of (Qnexa) treatment on risk for major adverse cardiovascular events in an obese at-risk population," FDA reviewers said about Qnexa.

The FDA staff said they would also ask the advisers whether Vivus needs to do a heart-focused study of Qnexa before it is approved. The FDA will make its final decision by April 17.

FDA staff said patients taking Qnexa during a clinical trial had lost more weight, and kept it off for longer, than those taking a placebo, or sugar pill. The Qnexa patients also had lower levels of problems associated with obesity, such as issues with blood pressure and blood sugar.

However, the FDA staff said patients taking the drug had more safety problems, including memory loss and higher heart rates, than those on a placebo, and some of these problems could get worse over time.

They also said exposure to one of the ingredients in Qnexa has been linked to a higher rate of birth defects in other studies.

REAL-WORLD PROBLEMS

Qnexa is a combination of appetite suppressant phentermine and anti-seizure drug topiramate.

A company study showed topiramate caused a higher rate of oral clefts in infants of women taking the drug during pregnancy, and the company said it would limit Qnexa to women who are not pregnant.

Vivus resubmitted its application to the FDA in October with more data and proposed to limit the drug to only women who cannot have children. In January, the company broadened the label to just limit pregnant women from taking it, in response to an FDA request.

Jason Butler, an analyst at JMP Securities, said the FDA's request to allow non-pregnant women to take the drug was a positive sign.

"The FDA is saying ... it's a small signal of risk, but it's not so great that we have to stop people using it," Butler said, adding he expected heart issues to be a greater concern.

However, in its review on Friday, the FDA staff said limiting the drug to nonpregnant women might be difficult in the real world, especially since 34 women got pregnant during the clinical trial.

Vivus is not the only company vying to get an obesity drug on the market.

Arena Pharmaceuticals and Orexigen Therapeutics have been pitching their own fat-fighters again to the FDA after rejections.

In February, Orexigen agreed with the FDA on the design of a 10,000-patient heart-safety trial required for the approval of its Contrave drug.

The FDA is also set to review Arena's lorcaserin by June 27, after rejecting it in October 2010 because of a potential cancer risk.

Drugmakers have struggled for years to develop weight-loss drugs that are both effective and safe.

Back in 1997, the infamous diet drug "fen-phen" was pulled from the market after reports of fatal heart-valve problems in some users. Another diet pill, Meridia, was pulled from the U.S. market in 2010 after being linked to heart problems.

The only prescription obesity drug currently approved for long-term use is Roche Holding AG's Xenical, which got the FDA's nod in 1999. GlaxoSmithKline markets a lower-dose, over-the-counter version called Alli. But both have their own problems, as they can cause serious liver problems, uncontrolled bowel movements and gas.

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