An experimental obesity pill from biotechnology company Vivus Inc appears to help people shed pounds, but concerns remain about its safety, U.S. Food and Drug Administration staff said in documents made public on Tuesday ahead of a public meeting on the drug later this week.

The Mountain View, California-based company wants to market its once-a-day pill, Qnexa, for use with diet and exercise. If approved, it would be the first new U.S. prescription weight-loss drug in a decade.

All three doses of the drug "were efficacious for weight loss," FDA staff reviewers said, but there are five areas of safety concerns, including the effect on pregnant women and psychiatric side effects such as depression.

There were also more reports of attention span, memory and language problems as well as of increased heart rate in Qnexa patients, the staff said in documents posted on the FDA's website. The potential for increased body acids was also a concern.

On Thursday, an FDA panel of outside experts will discuss the safety issues and offer advice on whether to approve Qnexa. The agency will make the final approval decision, which Vivus expects by October 28.

Arena Pharmaceuticals and Orexigen Therapeutics are also seeking FDA approval for their rival obesity pills, which face FDA panel reviews later this year.