The cost-effectiveness of acetaminophen, NSAIDs, and selective COX-2 inhibitors in the treatment of symptomatic knee osteoarthritis

Objective: The objective of this study was to conduct an economic evaluation of rofecoxib and celecoxib compared with high-dose acetaminophen or ibuprofen with and without misoprostol for patients with symptomatic knee osteoarthritis (OA). Methods: A decision analysis model was designed over 6 months using two measures of effectiveness: 1) number of upper gastrointestinal (GI) adverse events averted; and 2) number of patients who achieved perceptible pain relief. Separate analyses were conducted for all patients and for those who did not respond to acetaminophen. Outcome probabilities were obtained from a comprehensive review of randomized controlled trials and observational studies. Costs were derived from actual resource utilization of OA patients. Results: In terms of averting GI events, acetaminophen dominates the other options for an average risk patient population. For patients who did not respond to acetaminophen, rofecoxib had the lowest incremental cost-effectiveness ratio (ICER) per GI event avoided ($32,000) relative to ibuprofen. In terms of pain control, ibuprofen had an ICER of $610.77 per additional patient achieving minimal perceptible clinical improvement (MPCI) relative to acetaminophen, while rofecoxib had an ICER of $12,000 relative to ibuprofen. For patients who did not respond to acetaminophen and who are at high risk of developing an adverse GI event, rofecoxib dominates ibuprofen as the preferred alternative for both measures of effectiveness. One-way, two-way, and probabilistic sensitivity analyses established that these results were generally robust. Conclusions: Our results suggest that for average-risk knee OA patients, acetaminophen dominates the other therapies in terms of cost per GI event averted. In terms of pain relief, cost-effectiveness acceptability curves indicate that if one values pain relief below $275 per patient achieving MPCI, acetaminophen is the therapy most likely to be optimal; between $275 and $14,150, ibuprofen is most likely to be optimal; and above $14,150, rofecoxib is most likely to be optimal.