['To compare the efficacy of valdecoxib 40 mg q.d. (with a second dose on day 1) with diclofenac 75 mg b.i.d. in the treatment of acute low back pain.', 'This was a multicenter, randomized, double-blind study. Patients with acute low back pain, class 1a or 2a (Quebec Task Force), with a visual analog scale score >/=50 mm (on a 100-mm scale) and moderate to severe pain on a categorical scale, were randomized to valdecoxib 40 mg q.d. (with a second dose on day 1) or diclofenac 75 mg b.i.d. for 7 days (170 patients per group). The primary efficacy end point was change in pain intensity (visual analog scale, mm) from baseline to day 3 for the per-protocol population.', 'Least squares mean reductions in pain intensity from baseline to day 3 were similar for valdecoxib (-42.02 mm) and diclofenac (-41.43 mm). Valdecoxib was comparable to diclofenac as the lower limit of the 95% confidence interval of the estimated difference (0.59 mm; 95% confidence interval, -3.40 to 4.59 mm) was within the prespecified noninferiority margin of -10 mm. The overall incidence of adverse events was similar for valdecoxib (28%) and diclofenac (26%). No statistically different moderate or severe upper gastrointestinal adverse events were reported, although they were numerically greater for diclofenac (8) than for valdecoxib (3).'] Is valdecoxib as efficacious as diclofenac in the treatment of acute low back pain?