Severity of knee pain does not predict a better response to an antiinflammatory dose of ibuprofen than to analgesic therapy in patients with osteoarthritis.
OBJECTIVE
To determine whether greater pain intensity at initiation of treatment predicted better response to ibuprofen than to acetaminophen in subjects with knee osteoarthritis (OA).


METHODS
Data from 182 patients with knee OA who had taken part in a 4 week randomized, double blind, parallel comparison of 4,000 mg/day acetaminophen vs either 1,200 or 2,400 mg/day ibuprofen were reanalyzed using Pearson correlation coefficients for baseline pain severity, treatment assignment, and treatment response. Pain measures were visual analog scales for overall pain, resting pain, and walking pain. Baseline pain severity was divided into low, medium, and high tertiles, and treatment related differences in pain response were sought with pairwise t tests. Two-factor analysis of variance (ANOVA) models were used to seek interactions between baseline pain severity and treatment group, which would indicate differential drug treatment responsiveness.


RESULTS
Greater baseline pain predicted greater pain relief with all 3 treatments. Patients with a high level of baseline rest pain appeared to respond better to ibuprofen 2,400 mg/day than to the other treatments, but this difference was not evident after correction for multiple statistical tests. ANOVA did not reveal significant differences in response to the 3 treatments or a significant interaction.


CONCLUSIONS
Our data suggest that acetaminophen and ibuprofen are comparably effective in treating knee OA pain, even when the pain is severe.
Bradley
J D
JD
Department of Medicine, Indiana University School of Medicine, Indianapolis, USA.
Katz
B P
BP
Brandt
K D
KD
D000082:Acetaminophen / Q000008:administration & dosage*; D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage*; D000704:Analysis of Variance; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage*; D004311:Double-Blind Method; D006801:Humans; D007052:Ibuprofen / Q000008:administration & dosage*; D020370:Osteoarthritis, Knee / Q000188:drug therapy*; D010146:Pain / Q000188:drug therapy*; D010147:Pain Measurement; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D016896:Treatment Outcome
D018712:Analgesics, Non-Narcotic; D000894:Anti-Inflammatory Agents, Non-Steroidal; D000082:Acetaminophen; D007052:Ibuprofen