1997 Volume 20 Issue 3 Pages 288-291
The effect of pulsed output ultrasound (1 MHz) with on/off ratios of 1 : 2, 1 : 4 and 1 : 9 on transdermal absorption of indomethacin from an ointment was studied in rats. Ultrasound energy was supplied for between 10 and 19 min at a range of intensities (1.0-2.5 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. The highest penetration was observed at an intensity of 1.0 W·cm-2 and application time of 15 min. With pulsed output it was possible to use higher intensities of ultrasound without increasing skin temperature or damaging skin.
