Effect and usability of anti-inflammatory drug plasters for knee osteoarthritis: A crossover, double-blind, repeated...

The use of plasters is a well-accepted treatment with high adherence. However, the characteristics such as its cool feeling or extensibility favored by elderly have a possibility to contribute to clinical utility. The purpose is to examine the effect of anti-inflammatory drug plasters for knee osteoarthritis and the clinical preference of the patients for using plasters. We conducted a crossover, double-blind, randomized controlled trial (RCT) recruited 168 patients with knee osteoarthritis.

We included a "run-in-period" to evaluate the patients' preference among A (first-generation; methyl salicylate), B (second-generation; indomethacin), and N (base substrate for B) before the crossover sequence of two treatment periods with A and B plasters; four arms (N-A-B, A-A-B, N-B-A, and B-B-A) were made to compare the assessment of A, B, and N plasters. We used two measures: The Japanese Knee Osteoarthritis Measure (JKOM), for clinical functions, and the usability questionnaire to evaluate the clinical value of plasters.

At baseline, there were no significant differences in characteristics. The subjects in groups A and B showed improved overall JKOM scores at the end of each intervention. Comparison of the change of the mean difference showed that A and B were statistically significant improvement over N (-2.40, (95%CI = -3.58 to -1.21), -2.52, (-3.65 to -1.40)) but no significant difference between A and B - 0.13, (-1.14 to 0.89)). In network analysis for usability, twelve items were independent of JKOM's network structure and consisted of two domains. The analysis of usability showed that N and B were preferred over A significantly.

Both the first- and second-generation plasters were statistically superior to the base only, but no significant difference between two generations. The patient is surely aware of the effect of the drug itself, but the two feelings are important in the preference.