Enhancement of transdermal absorption of drugs by pulsed output ultrasound :

Effect of radiating area and frequency

Abstract

The effect of radiating area and frequency of pulsed output ultrasound with an on/off ratio of 1 : 2 on transdermal absorption of indomethacin from an ointment was studied in rats. Ultrasonication was produced by a commercially available ultrasound system approved for human use which has two different sizes of transducer, large head (4.4 cm²) and small head (0.7 cm²). We did not find any difference in transdermal absorption of indomethacin between two transducer (effective radiating areas). Ultrasound should be generated by a small head since a small head enalbes the rats to administer the treatment. The frequency of the pulsed ultrasound was suggested to play an important role in the transdermal phonophoretic delivery system of indomethacin ; 1 MHz appeared to be more effective than 3 MHz in improving the transdermal absorption.