Transdermal delivery of insulin by ultrasonic vibration.

Ultrasonic vibration has been used to deliver insulin through the skin of hairless mice fasted overnight and partially immersed in an aqueous solution of insulin (20 units mL-1). The skin surface was exposed to ultrasonic vibration in two ultrasonic energy ranges (3000-5000 Pa and 5000-8000 Pa) at 48 kHz for 5 min. Blood glucose concentration was measured before and after exposure to insulin and ultrasonic vibration. In the group subjected to the lower energy vibrations, blood glucose fell rapidly to reach 34 +/- 11.9% of control values in 120 min, while when the animals were exposed to higher energy vibrations, the fall in blood glucose was 22.4 +/- 3.9% of control values at 120 min. The values remained low for the length of the experiment (240 min). Those exposed to insulin alone or ultrasonic vibration alone revealed no significant change in blood glucose concentration. It is postulated that ultrasonic vibration may alter skin permeability resulting in the absorption of insulin. That the blood glucose decrease was greater at the higher of the two energy ranges, suggests this factor could control insulin delivery.