FDA approves use of new weight-loss drug

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The prescription weight loss drug Belviq has been on the market for less than a month and a new pill is already outshining it.

The FDA is approving the drug Qnexa.

It's showing amazing results in clinical trials, but comes with some warnings.

Patients in clinical trials dropped an average of 23 pounds and doctors say in most cases the lost weight slows or even ceases the development of serious diseases like hypertension and diabetes.

Dr. Jonathan Zonca of Ascent Family Practice says prescription diet drugs, in general, can be very helpful for people who don't experience side effects from them.

Qnexa combines the amphetamine phentermine, which suppresses your appetite, with a drug called topiramate, which makes you feel full. 

Some medical experts warn that topiramate,  marketed as the anti-seizure drug Topamax, has been linked to birth defects.

Patients should be carefully screened before taking any prescription diet drug.  Doctors also point out that diet drugs are only one part of an equation for good health that includes exercise and a proper diet.

Qnexa is recommended for obese patients with serious health problems or those with a body mass index above 27.

Doctors say anyone just looking to lose a few pounds should not seek prescription drugs as a solution.