A new 2-drug combination offers more than double the weight loss of Orlistat, the only drug currently FDA-approved for long-term obesity treatment. In a study appearing online in The Lancet today, researchers from Duke University Medical Center and other centers report that combining phentermine (approved for short-term obesity treatment) and topiramate (approved for epilepsy and migraine) resulted in obese volunteers shedding up to 10 percent of their body weight during the one-year study. Here’s a look at the study findings:
What is the CONQUER study? This clinical trial at 93 medical centers looked at the safety and effectiveness of the 2-drug combination. 2,487 overweight or obese patients with two or more weight-related disorders--high blood pressure, high cholesterol, type 2 diabetes or pre-diabetes, or excessive belly fat (abdominal obesity)--were randomly assigned to take a once-a-day controlled-release capsule containing a higher dose of the 2-drug combination, a lower dose, or a placebo, for 56 weeks, explains Kishore Gadde, MD, lead author of the study and director of Duke’s obesity clinical trials program. The study was funded by Vivus, which is seeking FDA approval to market the drug combination under the trade name Qnexa.
How much weight did the participants lose? The people who took the higher dose lost an average of 22 pounds, compared to 18 pounds for those on the lower dose and 3 pounds for those on the placebo. All of the volunteers also participated in an exercise and healthy lifestyle program.
How does the drug combo differ from olistat? Orlistat, sold under the brand name Xenical in the prescription version, and Alli over-the-counter, works by reducing absorption of fat by 33 percent, says Dr. Gadde. “It acts on the gut, so if you eat fatty foods, such as cheeseburgers, the unabsorbed fat goes out in your stool and you’ll be running to the bathroom to avoid leakage. The effects are so unpleasant that you don’t want to eat those foods, but it has no effect on hunger. Over a year, the average weight loss is about 6 to 7 pounds.” The 2-drug combination works on the brain, helping people feel full more quickly, so they eat less.
What are the benefits of combo therapy? Not only did people in the study treated with the 2-drug combination lose up to 10 percent of their body weight, but they also showed striking improvements in blood pressure, cholesterol and trigylceride levels, inflammatory markers, and for those with diabetes or pre-diabetes, blood sugar levels. In addition, participants were able to cut down on medications for high blood pressure or diabetes. Another benefit, says Dr. Gadde. “In the group receiving the combination therapy, fewer of the pre-diabetic patients progressed to full-blown diabetes during the study, compared to the placebo group.”
What are the risks? The main side effects reported in the study were constipation, dry mouth and a mild pins-and-needles tingling sensation. There was also a higher rate of anxiety and depression in people who received the drug combination, versus the placebo group, with those on the higher dose twice as likely to experience these problems as those on the lower dose.
Is the combination treatment available now? While these drugs are not FDA-approved for long-term obesity treatment, since they are approved in the US for other purposes, including short-term weight loss in the case of phentermine, any doctor can legally prescribe them “off-label” for long-term weight loss or any other purpose the MD deems medically advisable. These promising study findings are likely to lead to widespread use of the combination therapy for weight loss.
Who should consider combo therapy? "If someone is seriously overweight with obesity-related disorders, and has tried diet and exercise without success, this new approach provides another option besides orlistat and weight-loss surgery,” says Dr. Gadde. However, patients should discuss the potential risks and benefits with their doctor, make an informed decision, and if the two drugs are prescribed, be closely monitored for anxiety and depression, which are most likely to strike during the early weeks of treatment. Overall, the study authors conclude, “The combination of phentermine and tomiramate, with office-based lifestyle interventions, might be a valuable treatment for obesity that can be provided by family doctors."
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