BACKGROUND: Phase 3 clinical trial results reveal that Qsymia is a clinically 
effective long-term treatment for obesity, but whether this treatment is 
cost-effective compared to a diet and lifestyle intervention has yet to be 
explored.
OBJECTIVE: To quantify the incremental cost-effectiveness of Qsymia (phentermine 
and topiramate extended-release) for health-related quality of life 
improvements.
STUDY DESIGN AND METHODS: Estimates are based on cost and quality of life 
outcomes from a 56-week, multicenter, placebo-controlled, phase 3 clinical trial 
undertaken in 93 health centers in the US. Participants were overweight and 
obese adults (aged 18-70 years) with a body-mass index of 27-45 kg/m(2) and two 
or more comorbidities (hypertension, dyslipidemia, diabetes or pre-diabetes or 
abdominal obesity). The intervention was diet and lifestyle advice plus the 
recommended dose of Qsymia (phentermine 7.5 mg plus topiramate 46.0 mg) vs. 
control, which included diet and lifestyle advice plus placebo. The study was 
from the payer perspective. Costs included the prescription cost, medication 
cost offsets and physician appointment costs. Effectiveness was measured in 
terms of quality-adjusted life years gained (QALYs). The main outcome measure 
was incremental cost per QALY gained of the intervention relative to control.
RESULTS: Our base-case model, in which participants take Qsymia for 1 year with 
benefits linearly decaying over the subsequent 2 years, generates an incremental 
cost-effectiveness ratio (ICER) of $48,340 per QALY gained. Using the base-case 
assumptions, probabilistic sensitivity analyses reveal that the ICER is below 
$50,000 per QALY in 54 % of simulations. However, results are highly dependent 
on the extent to which benefits are maintained post medication cessation. If 
benefits persist for only 1 year post cessation, the ICER increases to $74,480.
CONCLUSION: Although base-case results suggest that Qsymia is cost-effective, 
this result hinges on the time on Qsymia and the extent to which benefits are 
maintained post medication cessation. This should be an area of future research.