Short-term treatment with topical diclofenac epolamine plaster in patients with symptomatic knee osteoarthritis:: pooled analysis of two randomised clinical studies

Background: Data from two randomised, double-blind, placebo-controlled studies were considered in order to investigate the efficacy and safety of a bio-adhesive plaster for topical administration containing diclofenac epolamine ( DHEP) in patients with symptomatic knee osteoarthritis ( OA). Methods: Patients with radiologically confirmed symptomatic knee OA were included. The 14-day treatment consisted of two daily applications of either DHEP or placebo plaster. The algofunctional Lequesne index and pain intensity, measured by means of the Huskisson's visual analogue scale ( VAS), were considered as main efficacy parameters. The main analysis of the pooled data was by intention-to-treat. Results: Of the 258 patients included, 235 completed the study. At the end of the study, the mean decrease in the Lequesne index was 35% in the DHEP group and 15% in the placebo group ( p < 0.0001). The mean decrease in pain intensity was 59.5% in the DHEP group and 29.9% in the placebo group. No interaction resulted between treatment and study effects ( p >= 0.2 whatever the test). The non-parametric Hodges-Lehmann estimator of the treatment effect resulted in a reduction of 21.9% for the Lequesne index and of 30.0% in pain intensity. The number needed to treat ( NNT) for at least a 50% reduction of pain was 3.0 and the effect size for pain was 0.75. Conclusions: Topical application of DHEP plaster was shown to be an efficacious and safe short-term treatment for symptomatic knee OA, reducing pain and increasing physical function and may be similar in efficacy to oral non- steroidal anti-inflammatory drugs ( as indicated by relative benefit data and NNT value).