Comparison the Efficacy of EMLA Cream versus EMLA with High Frequency Sonophoresis in Decreasing Onset Time to Topical Anaesthesia in Adult Volunteers: A Pilot Study

Sonophoresis or phonophoresis is a well-known transdermal drug delivery mechanism. Usage of high frequency ultrasound for sonophoresis was initiated in late 1950s while the usage of low-frequency sonophoresis was investigated significantly during the past two decades. The objective was to analyze the efficacy of high frequency ultrasound probe in the penetration of EMLA cream in decreasing onset time for topical anaesthesia in adult healthy volunteers.

A prospective, open labelled, comparative study was conducted on patients reporting at the Pain Clinic our institute. Subjects received the intervention USG probe with EMLA either on the left or the right hand based on a random number chart, with the other hand of the same subject acting as a control. In group USG, the probe was applied directly on the cream without any added pressure. Sensory testing was done every 10 minutes by pin prick on both the hands of the patients NRS scores of both the hands were recorded at 10.20,30 and 40 minutes.

Total 20 patients were selected for the study. Although a significant decrease in the pain scores in both the groups was observed after 40minutes, (p<0.05) both the groups are comparable at each point of time. We could not find any significant decrease in pain scores when groups are compared in intervals during the study period.

There is no significant difference in decreasing the intensity of pain scores upon application of ultrasound over EMLA in an adult population. Further studies have to be done to prove the efficacy in a larger population and pediatric ones