Ultrasound improves efficiency of transdermal drug delivery
By Ben Coxworth
September 17, 2012
Although some medications just don’t work when taken orally, the fact is that nobody likes getting injections. Research being conducted at MIT, however, could lead to a new painless method of drug delivery via the skin. Harsh though it might sound, it involves using ultrasound to blast off the outer layer of skin, so that drugs can then get into the bloodstream.
Experimenting on pig skin (which is very similar to human skin), researchers used a device that emitted both high- and low-frequency ultrasound waves into liquid placed against the skin. The ultrasound causes chaotically-moving bubbles to form in the liquid, which become unstable and implode upon reaching a certain size.
When they implode, the surrounding fluid rushes in to occupy the space they previously held, forming into “microjets” as it does so. These jets are sufficiently intense that they create microscopic abrasions on the adjacent skin. The medication, which is suspended in the liquid (which could be water) then no longer has the barrier of the tough outer layer of skin in its way, and is able to get into the patient’s system.
The process is reportedly painless, and the top layer of skin grows back in a few hours.
This isn’t the first time that scientists have looked at using ultrasound for this purpose, although previous efforts have concentrated solely on the use of low-frequency ultrasound, as high-frequency lacks the energy needed to make the bubbles implode. In those previous experiments, however, the abrasions were typically delivered in a scattered, non-uniform pattern.
In MIT’s approach, the abrasion pattern is much more evenly-distributed within the treated area, and thus better suited to drug delivery. This is partially because the high-frequency waves create additional bubbles, which can then be popped by the low-frequency waves. The lateral movement of the bubbles is also limited by the high-frequency waves, keeping them better confined within the target area.
In their experiments, the scientists used the technique to deliver either glucose or inulin (a carbohydrate) through the skin. Reportedly, however, it should be able to work for any medication currently administered by capsule, making higher doses possible. It should also be well-suited to the treatment of skin conditions, and to improve the effectiveness of transdermal patches, such as those that are currently used to deliver nicotine to people trying to quit smoking.
A smaller, hand-held version of the device is currently in the works. More information on the process is available in the video below.