Application of Ultrasound to Drug Therapy ; Transdermal Therapeutic System Using Pulsed Ultrasound

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The effect of pulsed ultrasound (1 MHz) with on/off ratios of 1 : 2,1 : 4 and 1 : 9 on transdermal absorption of indomethacin from and ointment was studied in rats. Ultrasound energy was supplied for between 10 and 19 min at a range of intensities (0.5-2.5 W cm^<-2>), energy levels commonly used for therapeutic purposes.The on/off pulsed ratio, intensity and the time of application were found to play an important role in the transdermal phonophoretic delivery system of indomethacin ; 1 : 2 pulsed output ultrasound appeared to be the most effective in improving the transdermal absorption of indomethacin. The highest penetration was observed at an intensity of 1.0 W cm^<-2> and time of application of 15min. With pulsed output it is possible to use higher intensities of ultrasound without increasing skin temperature. Progressively more skin damage was noted as the intensity and the time o application of ultrasound increased.When used at a proper intensity and time of application, pulsed ultrasound appears to be a safe technique for enhancing the passage of various drug molecules through human skin.