The Food and Drug Administration (FDA) has recently approved two new weight-loss drugs. They are Belviq (lorcaserin) and Qsymia (combination phentermine and topiramate).

These two new drugs do get some results. But each of them has drawbacks.

Belviq

• Weight loss: Half of the people who use this drug lose 5% of body weight, if they are obese to begin with. Half lose less weight than this. Hardly anyone loses more than 5%. People with diabetes lose less weight with this drug.
• Side effects: depression, migraine, memory lapses, lack of focus, low blood sugar reactions, fatigue and (in men) painful erections that last for many hours and may require emergency room treatment.

Qsymia

• Weight loss: an average of 15 extra pounds lost in the first year.
• Side effects: memory loss, suicidal feelings, heart rhythm problems and birth defects.

The FDA had earlier rejected Belviq because it caused tumors in animals. In June 2012, it was approved. However, it won't be available for another few months while the FDA considers what restrictions it will place on the drug. At high doses, it causes hallucinations, like the street drug LSD. There is concern that it may be used like a drug of abuse.

The other drug, Qsymia, combines two drugs that are already on the market, phentermine and topiramate (Topamax). Last year the FDA said it would not approve Qsymia because there was no long-term safety information. This year, with two years of safety data instead of one year, the FDA has given approval.

Also, Qsymia will be available only through a restricted program. The program must ensure that women taking this drug are using reliable birth control because Qsymia can cause birth defects.