Paresthesia is a common side effect of phentermine, Gadde noted, while the other side effects are most likely associated with topiramate.
An increased risk of depression and anxiety was also noted in those taking the drugs, seeming to increase as the dosage given rose. About twice the number of people in the high-dose drug groups dropped out of the trial compared to people receiving counseling alone, the researchers noted.
"If you see side effects like depression and anxiety, you need to be more careful," Gadde said. "You don't give these drugs to someone who is clinically depressed," he added.
According to Gadde, there were no birth defects among any of the babies born to the 34 women who became pregnant while taking Qnexa in this trial.
Ashley Buford, a spokeswoman for Vivus, said the company is hoping to resubmit its application for approval of Qnexa to the FDA by the end of the year.
Commenting on the study, obesity expert Dr. David L. Katz, director of the Prevention Research Center at Yale University School of Medicine, said that "this study shows what we had cause to believe before: that Qnexa facilitates weight loss beyond office-based counseling alone, as long as people are taking the drug."
However, the weight loss may be unlikely to persist if use of the drug stops, he said.
"In addition, we don't yet know if Qnexa is safe for long-term, or even lifelong use, and thus cannot yet say whether it is safe and useful for long-term weight control," Katz said. "Other drugs that have facilitated weight loss in the short term have failed to translate to safe and effective long-term use. This is the bar a truly useful weight-loss drug will need to clear," he said.
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