July 29, 2010 -- An experimental obesity drug that combines the antidepressant bupropion and the addiction drug naltrexone reduces body weight by 5% or more after one year when combined with healthy diet and regular exercise, according to a new report published online in The Lancet.
If approved, the new drug may be the right choice for dieters who get waylaid by their food cravings because it taps into the brain's craving and reward system in addition to curbing appetite. An FDA advisory panel is slated to review the drug, called Contrave, on Dec. 7. Manufacturer Orexigen Therapeutics, Inc. funded the new study.
In the 56-week study, participants received a high dose of the combination pill, a low dose, or a placebo twice a day. They were also advised to eat a low-calorie diet and engage in regular exercise. Those who took the higher dose of the new pill lost 6.1% of their body weight, while those who received the lower dose shed 5% of their body weight. By contrast, those people in the placebo group lost 1.3% of their body weight.
Fully 34% of people who took the high dose of the drug lost at least 10% of their body weight, compared with 11% who received the placebo.
Contrave Fights Cravings
The new combination pill is different than available weight loss medications in several important ways, says study author Frank L. Greenway, MD, a professor and chief of the outpatient clinic at Pennington Biomedical Research Center of Louisiana State University System in Baton Rouge, in an email.
"Both of the drugs in the combination are used to treat addictive disorders, naltrexone for opioid addiction and bupropion for smoking," he tells WebMD. "The combination of bupropion and naltrexone has been shown to work on both the appetite and the reward centers while other obesity medication has concentrated on the appetite mechanism alone," he says.
It may be "helpful for those people for whom craving interferes with their ability to stay on a diet," he says.
The drug is only effective for as long as people take it, he says. "When people stop taking a drug for a chronic disease like high blood pressure or obesity, the blood pressure or weight return to the levels they were prior to treatment."
No Serious Side Effects Seen
The most common side effects were nausea, headache, and dizziness. Each of the two drugs, when used separately, increases risk of certain psychiatric problems, but this was not seen with the combination pill. In addition, the two drugs, when taken as separate pills, also increase blood pressure.
Blood pressure did not decrease as much as would be expected with the 5% weight loss among people taking Contrave, and those in the placebo group saw sharper blood pressure reductions with just diet and exercise.
What's more, there were no changes seen in levels of LDL or "bad" cholesterol levels among those who took the experimental obesity drug. There were some improvements in other heart disease risk factors such as blood fats known as triglycerides, HDL or "good" cholesterol levels, insulin resistance, and C-reactive protein, a marker of inflammation.
"The reassuring thing about the side effects is that both of these drugs have been in wide use for over 20 years and no side effects were seen that were not expected from the experience with the individual drugs," Greenway says. "Bupropion-naltrexone improved insulin resistance [and] insulin resistance leads to diabetes and is associated with the cardiovascular risk factors associated with obesity."
In an accompanying editorial, Arne Astrup, MD, head of the department of nutrition at the University of Copenhagen, writes that "more data are needed to get a better overall assessment of cardiovascular risks of this otherwise promising combination therapy for obesity."
More Weight Loss Pills Needed
Combination pills represent the future of obesity treatment, says Louis Aronne, MD, director of the Comprehensive Weight Control Program at New York-Presbyterian Hospital/Weill Cornell Medical Center in New York City.
"Using medications and combination medications in conjunction with changes to diet and exercise can get us the results we are looking for in terms of reductions in body weight and obesity-related comorbidities," he says.
These medications are useful for people in whom diet and exercise alone is not enough but are not candidates for weight loss surgery, he says.
The more drugs available to treat obesity, the better, he says. It's not a one-size-fits-all situation.
"One medication may be right for one person and something else may be right for someone else," he says. "For a field to evolve, you need choices."
"People who have cravings might respond very well to Contrave," he says. There are no safety signals when it comes to mood, he says. "Nausea is the No. 1 side effect, and we have found that if we increase the dose gradually, we can reduce this risk." Aronne has conducted trials of the new drug.