A new method for accelerating the onset of the action of topical anesthetics by using the acoustic vibrations and near-infrared irradiations

Abstract

The topical anesthetics like as EMLA^® cream are widely used to prevent pain caused by certain skin treatment procedures. However, they need more than an hour to obtain the sufficient analgesic effect of the cream. In this study, we developed a new method for reducing the time until emerging the analgesic effect by topical anesthetics, by co-administrating both acoustic vibrations and near-infrared rays are generated by a physiotherapy apparatus.
F344/NSlc inbred rats under isoflurane anesthesia were used and the effects of the anesthetic cream (EMLA^®)were evaluated in terms of the latency of electromyography activities induced by the avoidance behaviors to noxious thermal stimulus on their tails. The cut-off period was set as 30 seconds to prevent serious tissue damage. In control rats with EMLA^® cream-coated tails wrapped with sealing film, a significant anesthetic effect was observed 20 minutes after the application (p<0.05) Conversely, in experimental rats given both acoustic vibrations and near-infrared irradiations in addition to EMLA^® cream application, a significant anesthetic effect was achieved after only 5 minutes (p<0.05) These results indicated that the acoustic vibrations and near-infrared irradiations accelerated the onset of the action of topical anesthetics. Although further optimization of parameters is required, this method would have a potential early clinical applicability.