INFLUENCE OF LOCALLY APPLIED HEAT ON THE PERFORMANCE OF TRANSDERMAL DICLOFENAC SODIUM PLASTERS

Objective: Applied heat to dermatologic preparations influences the medicine's performance, such as drug release rate and drug absorption. However, there is little information concerning the performance of non-steroid anti-inflammatory drug plasters at high temperature. Therefore, this study aimed to evaluate the effect of heat on drug dissolution and skin permeation from two kinds of Diclofenac sodium (DF) plasters In vitro, as well as transdermal absorption in healthy adult volunteers. Methods: DF dissolution tests were performed using the paddle-over-disk method with 500 mL of phosphate-buffered saline at 32 and 41°C. DF permeation was studied at 32 and 41°C using a Franz-type cell with Yucatan micropig skin (YMP). Moreover, eight healthy volunteers were tested two times for each preparation while receiving a piece of DF plaster, and then the same plaster with a heat-generating pad over 4 hours maintained at 40-41°C; then, the residual amount of DF in the plasters was evaluated. Results: Significant differences in the cumulative amount released from the preparations were seen between 32 and 41°C. The cumulative amount that permeated across YMP skin from all preparations at 32°Cwas also significantly higher than that obtained at 41°C. Furthermore, heat application on the plasters resulted in 1.4-fold higher absorption amount than without heat in the clinical study. Conclusion: This study indicated that locally applied heat caused rapid and substantial drug release, resulting in increased transdermal absorption of DF compared with that upon the use of the plaster without heat