This post is an abridged version of a blog published by Consumer Reports on May 5, 2016. See the original post here.
Consumer Reports recently worked with us to investigate the benefits and side effects of a new weight loss drug, Contrave. A drug that safely melts the pounds away would be a dream come true, but our analysis shows that the prescription weight loss pill Contrave is not that miracle drug.
In three clinical trials, people who took Contrave up to 56 weeks lost only five to nine pounds more on average than those who took a placebo. And Contrave can cause serious side effects, such as liver damage, seizures, and possible heart risks. That's why Consumer Reports' medical advisers say most people should skip it: such a small amount of weight loss is not worth the risk of those possible side effects.
Contrave is actually two older drugs, combined: the antidepressant bupropion (Wellbutrin and generic), and the addiction-treatment drug, naltrexone (ReVia and generic). We wanted to check how well Contrave measured up on both of those—or didn't. The FDA approved Contrave in late 2014 to be used along with a reduced-calorie diet and exercise, in those people who are either obese or who are overweight and have another serious condition, such as heart disease, high blood pressure, high cholesterol, or type 2 diabetes.
One of the largest clinical trials to date of Contrave shows obese and overweight people who took the drug for up to 56 weeks lost an average of 12 pounds (or about 5 percent of their body weight), compared with an average of 3 pounds (or 1 percent of their body weight) among those who took a placebo. Both groups were also put on a reduced calorie diet, exercised, and received behavioral counseling.
In another study, obese and overweight people who took Contrave for up to a year shed an average of 18 pounds (or 8 percent of their body weight) while the placebo group lost 11 pounds (5 percent of their body weight). Both groups were also put on a reduced calorie diet, exercised, and received behavioral counseling. The result is that Contrave contributed to losing an additional 7 pounds.
And the findings were even less impressive for people who had diabetes. Overweight people with that disorder who took Contrave for up to a year dropped an average of 9 pounds or 4 percent of their body weight, while those who took a placebo lost 4 pounds, or 2 percent of their body weight. In that case, Contrave helped people lose only 5 additional pounds.
Also, not everyone who takes Contrave will experience meaningful weight loss: In one trial, about 42 percent of people who took Contrave lost 5 percent or more of their weight compared to 17 percent of those who took a placebo.
Nearly 1 in 4 people in the clinical trials stopped taking the prescription weight loss pill because they couldn’t tolerate the common side effects, including nausea, headache, and vomiting. Contrave can also cause increased blood pressure, anxiety, and insomnia. Other side effects include constipation and dizziness.
Like other drugs that contain the antidepressant bupropion, Contrave carries a black-box warning—the strongest type issued by the FDA. Although Contrave is not intended for those under the age of 18, the warning states that the drug can, in rare instances, increase suicidal thoughts and behaviors in adolescents and young adults. It could also cause mania and depression to return in people who have previously suffered from those conditions. Other rare but serious side effects include seizures and a condition where eye pressure rises rapidly (angle-closure glaucoma).
The FDA was particularly concerned that Contrave might also raise the risk of heart problems, such as heart attack and stroke, so it required the manufacturer, Orexigen, to conduct a clinical trial to figure out if the drug is safe for the heart. But Orexigen has started and stopped two heart trials before they were finished. Now, the company says it plans to launch a third trial, but the results aren’t expected to be available until 2021.
In the meantime, the FDA still approved the drug without requiring the trial be completed, so Contrave remains available in the U.S. while its effect on the heart is still being investigated.
In a statement to Consumer Reports, Orexigen Therapeutics, said preliminary data from its first heart risk trial “provide valuable information and support our confidence in the overall safety for Contrave.”
However, the FDA told us that Contrave's heart risks remain unknown. Eric Pahon, a spokesman for the FDA, said it was premature to draw any conclusions from Contrave's first heart trial, so determining whether Contrave poses a risk to the heart will require completing the new study.
Steven Nissen, M.D., chair of Cardiovascular Medicine at the Cleveland Clinic, who led one of the trials, agrees with the FDA. “We don’t have a definitive answer about the safety of this drug and we won’t have one for a very long time,” he says.
For most people, the limited benefit of Contrave isn’t worth the risk of side effects or unknown heart risks, so our medical advisers recommend skipping it. To be sure, our analysis suggests that Contrave can help people lose a meaningful amount of weight, if they are able to tolerate it and stick with an exercise and reduced-calorie diet over the course of a year. But they would also expose themselves to the serious risks of the drug.
Also good to know: If you still decide to try Contrave, and haven’t dropped at least 5 percent of your weight after three months of taking the drug at the target dose, you should stop taking it because it’s unlikely that you ever will, according to information on Contrave's drug label.
Editor's Note: This article and related materials are made possible by a grant from the state Attorney General Consumer and Prescriber Education Grant Program, which is funded by the multistate settlement of consumer-fraud claims regarding the marketing of the prescription drug Neurontin (gabapentin).