There may be new hope for people looking for a diet pill that's both safe and effective.
Researchers found that participants in a clinical trial who took the drug Contrave for more than a year lost an average of 6.1 percent of their body fat. Trial participants who took Contrave began losing weight four weeks after starting the drug and maintained their weight loss throughout the 56 weeks of the study.
Researchers and some other experts say Contrave, which is a combination of the drugs naltrexone and buproprion, reflects a growing trend toward the development of weight-loss drugs made up of more than one active ingredient that could be more effective and safer than drugs that were once available or currently available. A panel from the U.S. Food and Drug Administration will review Contrave on Dec. 7.
Both naltrexone and buproprion have been around for some time and are used to treat different conditions. Buproprion is also known as Wellbutrin and is a common treatment for depression. Naltrexone is used to help people quit smoking or overcome drug addiction.
Contrave works on the same biological systems that control mood and appetite, and it's the first drug to combine buproprion and naltrexone as a way to lose weight. Researchers believe the main reason for the effectiveness shown in the clinical trial is the use of the two medications that target different areas involved in weight loss.
"We have to hit multiple points for better weight loss," said Dr. Ken Fujioka, a study co-author and director of the Center for Weight Management, Scripps Clinic. Fujioka is also on the advisory committee for Orexigen, the company that manufactures Contrave.
Nausea was the most common side effect. Trial participants also experienced headache, constipation, dizziness, vomiting, dry mouth and a temporary increase in blood pressure.
Dr. Kevin Niswender, assistant professor of medicine at the Vanderbilt University School of Medicine, said other side effects are possible with this drug.
"Whenever you target systems involved with mood, you have mood-related side effects," he said. Niswender had no involvement in the Contrave clinical trial.
"There were no signs of depression or suicidal thoughts in trial participants," said Fujioka.
Side effects have been the primary obstacle to pharmaceutical companies being able to keep weight-loss drugs on the market.
Since the FDA approved phentermine back in 1959, there wasn't another weight-loss drug approved until Redux in the 1990's.
That drug was ultimately pulled from the market in 1997 because of the association of its main ingredient, fenfluramine, with valvular heart disease.
Links to cardiovascular disease also doomed fen-phen, a combination of fenfluramine and phentermine. Fen-phen was also pulled from the market in 1997.
The demise of fen-phen illustrates perhaps the most daunting challenge to developing a diet drug -- combining efficacy with safety. While its side effects were very serious, fen-phen worked well.
"Fen-phen was probably the most effective medication we've had to date," said Dr. Robert Kushner, director of the Center for Lifestyle Medicine at Northwestern Memorial Hospital. Kushner is also an adviser to Orexigen.
There isn't an easy explanation for why there have been numerous high-profile diet drug failures.