New Diet Drug Hits the Market
PHOTO: The FDA has proceeded with caution with the approval of the first new weight loss drugs in more than 10 years.

With more than 36 percent of American adults now classified as obese according to the Centers for Disease Control and Prevention, and the numbers still climbing, doctors are clamoring for more pharmaceuticals to treat their patients.

Last year, the Federal Drug Administration obliged by approving the first new weight-loss drugs in more than a decade. The first, Qsymia, has been available with a prescription for nearly 10 months while the second, Belviq, will be available by prescription starting this week.

Is obesity the last acceptable prejudice?

But even as doctors have begun scribbling prescriptions for these new weight loss medications, many dieters remember the long and checkered past of diet drugs in this country. Some drugs that were originally viewed as rock stars for weight loss and appetite control were ultimately pulled off the market after it was found they posed serious health risks.

Amphetamines

In the 1950s amphetamines were the most widely used weight-loss medications, available by prescription and in some over-the-counter products. This class of drugs works by stimulating the central nervous system to both suppress appetite and boost metabolism.

Dieters found them to be quite effective. Unfortunately, they were also highly addictive and carried some critical side effects.

"Once people stopped losing weight they would take more and more of the pills, and this left some feeling racy and agitated with a rapid pulse and high blood pressure," said Dr. Louis Aronne, a New York-Presbyterian/Weill Cornell physician who specializes in weight loss and weight-loss research.

How young is too young to diet?

By the 1970s, the FDA limited its use for weight loss to short-term treatment only. Aronne cautioned that buyers must still beware: Amphetamines are still hidden in some unregulated foreign weight-loss supplements that can be readily purchased over the Internet.

Fen-phen and Redux

In 1992, a small study found that those who dieted, exercised and took a pill that combined two existing appetite suppressants, fenfluramine and phentermine, lost an average of 16 percent of their body weight. The combination drug, dubbed fen-phen, became a huge hit with the dieting public.

Riding the wave of the supplement's popularity a similar drug named dexfenfluramine and marketed as Redux was quickly approved by the FDA in 1996. Physicians were soon writing 85,000 prescriptions a week for Redux while consumers were gobbling up mail order and over the counter fen-phen.

The drug crashed and burned less than two years later, when FDA reports linked both fen-phen and Redux to heart valve defects, pulmonary hypertension, a sometimes fatal lung condition and sudden death. Animal studies also found that fen-phen caused brain damage in lab animals.

"It turned out there was a good "phen" and a bad "fen," said Dr. Marina Kurian, the medical director at the NYU Langone Weight Management Program at the New York University School of Medicine. "Phentermine has since been thoroughly studied and found to be safe."

Sibutramine (Meridia)

Sibutramine suppressed appetite and blocked the reuptake of neurotransmitters to trick the brain into thinking the stomach was full. Approved in 1997, the drug was found during clinical trials to increase heart rate and blood pressure. Since weight loss reduces these symptoms, however, experts believed the drug's benefits would balance out its side effects.

Weight- loss surgery alternatives

In 2010, the FDA asked the drug's maker, Abbott Laboratories, to voluntarily withdraw the diet pill from the market. The drug's risks proved not to be worth the benefits: Studies found a 16 percent increase of major cardiac events in patients taking Meridia compared with those who weren't taking the drug, with a negligible difference in weight loss. Abbott complied with the request.

Orlistat

Orlistat, sold in prescription form as Xenical and over the counter under the brand name Alli, is still available but according to Aronne, has never caught on with dieters.

Rather than working on the brain, it targets the gut, preventing the absorption of fat. Used in combination with a low-fat diet and exercise program, studies find it can help drop 50 percent more weight than diet and exercise alone.

All that sounds good -- until you get to the side effects, which Kurian said include a charming phenomenon known to some as "anal soilage."

"You go to pass gas but it's a wet, stinky gas that soils your underwear. It can be really embarrassing," Kurian said.

GlaxoSmithKline, the maker of both Alli and Orlistat, acknowledges these side effects on its website, stating, "Diet-related side effects are bowel movement changes that are most commonly caused by eating meals with too much fat while using alli capsules. Such effects may include oily spotting, loose stools and more frequent stools that may be hard to control."

In studies, only about 50 percent of users experienced any gastrointestinal distress from using either medication. Aronne pointed out that these nasty side effects occur only after eating a meal high in fat. Rather than forgo the fat, many consumers choose to skip their pill instead. Done often enough, the drug is not as effective and weight loss is minimal.

Qsymia and Belviq

Both Qsymia or Belviq have already been thoroughly tested and will continue to be tested and monitored for years to come.

"As part of approval commitment, we are required to study the drug for up to five years to exclude cardio vascular risk," Dr. Gary Palmer, chief medical officer at Eisai, the company that is marketing Belviq in the U.S.

Peter Tam, president of Vivus, the company that markets Qsymia, said the FDA took a very conservative approach to approval of both drugs. He stressed that Qsymia is a serious medication for patients who have metabolic disease that will improve along with weight loss.

"It's not for frivolous use," he said.

No Miracles Here

Neither drug appears to be a magic bullet.

Belviq is approved for the obese and those who are overweight and have other serious health risks. It targets the serotonin receptors in the brain to help patients feel full. In clinical trials, the average person lost 3 percent to 3.7 percent of his weight after taking Belviq for a year compared to those taking a placebo. Those without type 2 diabetes averaged over 5 percent weight loss.

The FDA said patients should stop taking Belviq if they fail to lose 5 percent of their body weight after three months of use. Patients are unlikely to see any significant weight loss by staying on the drug, the agency said.

Qsymia -- a combination of and topiramate, a drug commonly prescribed for migraines and as an anti-seizure medication, and phentermine -- performed better in clinical trials. About half of the 4,430 overweight and obese patients in the Qsymia studies on the recommended dosage lost an average of 10 percent of their weight in the first year of taking the drug.

Coming up with a safe, highly effective diet drug is hard, Aronne said, because obesity is such a complex condition.

"We're not just talking about taking a pill here. We are talking about taking a pill to fix what's busted -- the circuitry of the brain that misreads the signals of appetite, fat storage and other factors. We still don't know why this is so difficult."

More ABC News