The report is published in the April 11 online edition of The Lancet.
In this multicenter trial, called CONQUER, Gadde's team randomly assigned almost 2,500 overweight and obese men and women to diet and exercise counseling alone or to counseling alongside once-daily low- or high-dose Qnexa in pill form. Low-dose Qnexa contained 7.5 milligrams (mg) of phentermine and 46 mg topiramate, while the high-dose pill contained 15 mg of phentermine and 92 mg of topiramate.
After 56 weeks, patients on either dose of Qnexa had lost significantly more weight than those who only took part in the counseling program, the researchers found.
Those not taking the combo drug had an average weight-loss of 3 pounds, compared with 18 pounds for those on low-dose Qnexa and 22 pounds for those on the high-dose Qnexa.
Moreover, while 21 percent of those in the counseling program alone lost at least 5 percent of their weight, that number rose to 62 percent of those on low-dose Qnexa and 70 percent for those on the high-dose regimen.
In addition, people taking Qnexa saw reductions in their blood pressure, blood cholesterol levels, triglycerides (a blood fat) and blood sugar levels, Gadde's group found.
The ideal candidates for this treatment are obese and overweight people whose weight is affecting their health, Gadde said.
"When you are looking for weight-loss in patients, it shouldn't be for cosmetic reasons," he said. "An ideal candidate for weight-loss is someone that has obesity-related [health] risks."
Gadde noted that the weight-loss seen in the first year of the trial was maintained in the second year of the trial.
Side effects did occur in some patients, and were especially common at the higher dose. In those taking high-dose Qnexa, the most common side effects were dry mouth (21 percent), paresthesia, or a feeling of "pins and needles" (21 percent)
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