A combination of bupropion and naltrexone appears to be an effective treatment for weight loss in obese patients. Contrave, manufactured by Orexigen Therapeutics, was found to produce a 6.1% loss of body weight over the 56-week trial for those on the highest dose. An FDA panel will review the new weight loss drug on December 7th.
Contrave is a sustained release formulation combining two currently approved drugs. 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 is different than other currently available weight loss medications in several important ways, says study author Frank L. Greenway, MD, professor and chief of the outpatient clinic at Pennington Biomedical Research Center of Louisiana State University System.
“Both of the drugs in the combination are used to treat addictive disorders, naltrexone for opioid addiction and bupropion for smoking,” says. “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. This may be “helpful for those people for whom craving interferes with their ability to stay on a diet,” he says.
The Contrave Obesity Research (COR-1) study, the largest of four phase III trials involving the weight loss drug, enrolled 1742 patients between the ages of 18 and 65 (mostly women) who had either a body mass index (BMI) above 30 and were without complications, or a BMI of 27 and above with dyslipidemia or hypertension.
Patients were randomized to a placebo or to a pill containing 360 mg of bupropion plus either 16 or 32 milligrams of naltrexone. Dosing was once a day for 56 weeks. The patients also received instruction for a healthy diet and exercise plan.
In addition to producing a measureable weight loss, the drug also brought significant improvements in HDL cholesterol, triglycerides, and C-reactive protein compared with a placebo. Fasting insulin and glucose were also improved among those on the highest doses of naltrexone.
The most frequent adverse event in the treatment groups was nausea, occurring in almost 30% of patients. Headache, constipation, dizziness, vomiting, and dry mouth were the other more common symptoms reported.
Contrave is one of three new investigational diet drugs that are seeking market approval this year. Recently an FDA panel reported concerns about the safety of Qnexa, a combination of phentermine and topiramate. They have not yet reviewed Lorcaserin which works by increasing a brain chemical (serotonin), leading to increased satiety.