An analgesic model for assessment of acute pain response in osteoarthritis of the knee

BACKGROUND: Osteoarthritis (OA) is frequently treated only during periods of flare, in which rapid onset of analgesia is the outcome target. OBJECTIVE: To assess an acute pain model of knee OA in flare. METHODS: In a multicenter, randomized, double-blind, controlled study, 530 patients aged >or=50 years received valdecoxib 10 mg qd (n=212), rofecoxib 2 5 mg qd (n=208), or placebo (n=110). Pain intensity (PI) was measured on a visual analog scale (VAS) at baseline after a 10-min walk. Patients took their first dose of study medication, rested for 20 min, then measured their PI VAS at 0.5, 1, 1.5, 2, 3, 4, 5, and 6h, each time following a 10-min walk. RESULTS: PI VAS differences (PID) were significantly greater vs placebo both with valdecoxib and rofecoxib (P<0.05) beginning as early as 3h (intent-to-treat population). The percentage of patients with analgesia onset from 4h was significantly higher with both valdecoxib (55%) and rofecoxib (56%) relative to placebo (40%). Median time to first onset of analgesic was shorter with both valdecoxib and rofecoxib compared with placebo (P=0.104 vs valdecoxib; P=0.036 vs rofecoxib). CONCLUSIONS: This acute pain model of knee OA flare detected significant pain relief with agents known to relieve pain in OA and placebo within hours after the first treatment dose, allowing assessment of pain relief within hours rather than days or weeks when evaluating analgesic efficacy in OA. This model is undergoing further study to determine optimal walk times, distances, and rates to maximize its sensitivity.