Cost-effectiveness analysis of allopurinol versus febuxostat in chronic gout patients: a U.S. payer perspective

Abstract

Background: Gout is a chronic inflammatory condition associated with poor urate metabolism. Xanthine oxidase inhibitors such as allopurinol and febuxostat are recommended to reduce uric acid levels and to prevent gout attacks in adult patients. Under budget-driven constraints, health care payers are faced with the broader challenge of assessing the economic value of these agents for formulary placement. However, the economic value of allopurinol versus febuxostat has not be assessed in patients with gout over a 5-year time period in the United States.

Objective: To evaluate the cost-effectiveness of allopurinol versus febuxostat in adult patients with gout over a 5-year time period from a U.S. health care payer's perspective.

Methods: A Markov model was developed to compare the total direct costs and success of serum uric acid (sUA) level reduction associated with allopurinol and febuxostat. Treatment success was defined as patient achievement of a sUA level less than 6 mg/dL (0.36 mmol/L) at 6 months. Event probabilities were based on published phase III randomized clinical trials and included long-term sequelae from open-label extension studies. A hypothetical cohort of 1,000 adult gout patients with sUA levels of ≥ 8 mg/dL (0.48 mmol/L) who had received either allopurinol 300 mg or febuxostat 80 mg at model entry transitioned among the 4 health states defined by treatment success, treatment failure and switch, treatment dropout, and death. The length of each Markov cycle was 6 months. Costs were gathered from the RED BOOK, Medicare fee schedules, Healthcare Cost and Utilization Project's Nationwide Inpatient Sample, and for a limited number of inputs, expert consultation. Direct costs included treatment drug costs, costs for prophylaxis drugs, diagnostic laboratory tests, and the treatment and management of acute gout flare. Resource utilization was based on clinical evidence and expert consultation. All costs were inflated to 2014 U.S. dollars and were discounted at 3% in the base case. One-way sensitivity analysis and probabilistic sensitivity analyses (PSAs) were performed to assess the robustness of the results.

Results: The total per patient cost incurred over 5 years was $50,295 for febuxostat and $48,413 for allopurinol, with an incremental total cost of $1,882. The expected percentage of treatment success during the 5-year period was 72 for febuxostat and 42 for allopurinol, resulting in an incremental percentage of treatment success of 30. The estimated incremental cost-effectiveness ratio for febuxostat compared with allopurinol was $6,322 per treatment success over a 5-year time period. The one-way sensitivity analysis indicated that the results were sensitive to probability of treatment success for allopurinol, probability of treatment dropouts for both allopurinol and febuxostat, and the probability of failure and switch to allopurinol. PSAs demonstrated that at a willingness-to-pay threshold of $50,000 per treatment success, febuxostat was cost-effective compared with allopurinol.

Conclusions: Febuxostat was found to be a cost-effective option compared with allopurinol based on a U.S. payer perspective.

FIGURE 1

Markov Model of Allopurinol Versus Febuxostat Depicting Health States (Simplified) ^a,b

FIGURE 2

Tornado Diagram of One-Way Sensitivity Analyses Showing Influence of Base-Case Costs and Probabilities ^a

FIGURE 3

Cost-Effectiveness Acceptability Curve: Febuxostat Versus Allopurinol for Treatment of Adult Gout Patients ^a