It was noted that both dose combinations were well tolerated over the 6 months of the phase 3, randomized, double-blind, placebo-controlled study. The researchers randomized 756 patients to 1 of 7 treatment groups. The 4 single-drug groups were treated with Phentermine at 7.5 or 15 mg, or Topiramate CR at 46 or 92 mg. The 2 combination groups received VI-0521 7.5/46, which contained Phentermine 7.5 mg plus Topiramate CR 46 mg, or VI-0521 15/92, which contained Phentermine 15 mg plus Topiramate CR 92 mg. A seventh group received placebo.

In addition to the drug treatment, all patients were given lifestyle and exercise advice and followed a diet that cut their calories by 500 kcal/day. The mean age of all patients was 45.6 +- 11.9 years and 79% were women.