A new treatment for obesity that combines two existing drugs resulted in twice as much weight loss as the only approved long-term anti-obesity medication, according to a study released Monday.
A mix of Phentermine and topiramate, sold under the brand name of Topamax, was shown in clinical trials to be twice as effective as orlistat, which is commercialised in some countries as Xenical or Alli, it said.
The drug combo appears to have additional health benefits, including improved "markers," or indicators, for blood pressure, sugar levels, lipids and inflammation, it added.
Phentermine is the most widely prescribed short-term weight drug in the United States.
Topiramate is an anticonvulsant approved for treating seizure disorders and migraines. It has been shown to work well for weight loss in obese patients with type 2 diabetes, but - taken alone - has also been linked to cognitive and psychiatric side effects.
Lower doses taken with a controlled-release mechanism and in combination with other drugs would likely reduce those side effects, tests have shown.
Led by Kishore Cadde of the Duke University Medical Centre, in Durham, North Carolina, the new trial was conducted over 20 months with nearly 2,500 overweight or obese adults with at least two major health-risk symptoms.
The patients were divided into three groups.
One was given a once-a-day dose of 7.5 mg of Phentermine and 46 mg of topiramate, while a second group was given 15 and 92 mg of the same drugs, respectively.
The third group were given look-alike placebos.
After 56 weeks of treatment, the low-dose group dropped, on average, 8.1 kilos (18 pounds) while the high-dose group shed 10.2 kilos (22 pounds).
Patients given placebos lost 1.4 kilos (3.0 pounds).
Overall, 62 percent of the low-dose patients lost at least five percent of body weight, while 70 percent in the high-dose cohort crossed the same threshold.
Patients given placebos lost 1.4 kilos (3.0 pounds), with 21 percent sloughing five percent off their total weight.
The two-drug treatment was well tolerated physically, with only sporadic cases of dry mouth and constipation, according to the study, which is published by The Lancet.
The high-dose group, however, showed a higher dropout rate due to adverse cognitive and psychiatric reactions.