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.