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| Ultrasound waves of two different frequencies generate tiny bubbles of water on the skin's surface. When these bubbles pop, the skin's surface is lightly worn away, allowing drugs to pass through the skin more easily--Graphic courtesy of Carl Schoellhammer |
Delivering drugs through the skin is an easy option for patients, but it can be tough to achieve. However, ultrasound, perhaps better known for imaging unborn babies, could get skin to be more "transparent" to drugs, making the whole process easier and more efficient, according to research from the Massachusetts Institute of Technology.
Different teams have used ultrasound to make skin more permeable to drugs. It acts by gently and painlessly wearing away the top layer of the skin through sound-triggered movements in fluids. But it's not always been successful, and increasing the length of time or the intensity of the ultrasound treatment can just make the skin too hot.
A team of MIT engineers has upped the efficacy of the ultrasound by simply adding in another frequency. The combination of low-frequency and high-frequency ultrasound gently abrades the skin more evenly, allowing more of the drug to pass through, and the skin remains more permeable for 24 hours, which allows extended and controlled delivery of drugs.
With pig skin, the team was able to improve the delivery of glucose tenfold and inulin (a carbohydrate) fourfold and the researchers believe that they will be able to make the delivery even better. The technique could be used to enhance the activity of existing transdermal patches, allowing the delivery of complex molecules like insulin--freeing diabetics from daily injections--or to deliver vaccines to the skin. It could also be used in developing countries, as its use requires less intensive training than the use of shots.
"This could be used for topical drugs such as steroids--cortisol, for example--systemic drugs and proteins such as insulin, as well as antigens for vaccination, among many other things," says Carl Schoellhammer, one of the lead authors.
The researchers are developing a prototype hand-held ultrasound device. While this process looks like a possibility on tests of pig skin on the lab bench, it hasn't yet been studied in animals or humans, so there will still be a way to go before a blast of sound gets complex drugs like insulin right under the skin.
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