[A comparison of leflunomide and subcutaneous methotrexate in the treatment of rheumatoid arthritis: an approximation based on the number needed to treat].

Objective: To compare, in the Spanish setting, two drugs for adults with rheumatoid artritis (RA): leflunomide and subcutaneous methotrexate (SC). The high price of methotrexate SC compared with traditional presentations of methotrexate justifies conducting an economic evaluation comparing it with leflunomide.

Methods: The analysis considered the annual costs of the drugs and their effectiveness, measured with a Number Needed to Treat (NNT) approach, considering both the ACR20 and ACR50 criteria for effectiveness. Data about efficacy and dosage were derived from the clinical trial US310, a randomized, doble-blinded controlled trial, which compared efficacy and safety of leflunomide (20mg/daily) vs placebo vs methotrexate (7.5-15mg/weekly) in 482 patients with active RA. Data about use of medical resources for drug monitoring (visits to rheumatologists and diagnostic procedures) were derived from the manufacturers' summary of product characteristics. Direct costs (drugs and monitoring) were obtained from two Spanish databases. The analysis has been performed under the Spanish National Health System perspective.

Results: Using the ACR20 criteria, the NNT with leflunomide and methotrexate are 4 (95% CI, 2.56-7.71) and 5 (95% CI, 3.03-14.3) respectively. Using the ACR50 criteria, NNT are 4 (95% CI, 2.72-6.54) and 7 (95% CI, 4.03-19.3). In the case of leflunomide, annual treatment costs per patient-year equals 1,793.30€; in the case of methotrexate total treatment costs amounts to 2,149.20€.

Conclusions: Combining these results the cost of a controlled patient according to ACR20 would amount 7,173€ for leflunomide and 10,746€ for methotrexate SC. Results considering ACR50 are 7,173€ and 15,044€ for leflunomide and methotrexate respectively.