People who dislike hypodermic needles may soon get their medicine with less anxiety, thanks to UCSB research.

Chemical engineering Assistant Professor Samir Mitragotri and his team of researchers have evaluated a number of transdermal drug delivery methods similar to those used in the nicotine patch. By testing a large number of different methods rapidly, a special combination of chemicals was found that causes minimal skin irritation and allows the drug to pass through the skin.

Delivering drugs transdermally with a patch is often more desirable than with a hypodermic needle because the drug can be released over a long period of time and the patient can easily apply the drug at home. The problem is that drug molecules are sometimes too large to pass directly through the skin.

In order to facilitate the drug’s movement through the skin, the patches also contain penetration enhancers, chemicals that cause the skin to be more permeable. The problem is that the enhancers sometimes cause irritation to the patient.

Mitragotri found that by mixing different enhancers together, a more potent compound could be created that also causes less irritation. The increased potency of the enhancer means that drugs which are typically harder to pass through the skin can now be used in a patch.

Currently, patches are commonly used for birth control and as an aid to quit smoking. These are good applications for slow transdermal delivery because the drug is best delivered over a long period of time. In contrast, a single injection of the drug has a high initial concentration, then tapers off relatively quickly.

Mitragotri tested thousands of different combinations looking for one specific blend that would be the most efficient with the least irritation. The initial testing process is general, testing only to see the effectiveness of a particular blend.

Those chemical blends that showed promise were then screened for their potential to irritate the skin. Finally, hairless rats served as the final test in determining the chemicals’ overall safety.