Transdermal drug delivery has proven highly successful in a number of applications, significantly reducing the risks associated with injection or medical therapies, notably in pain management and HRT.
However, it can only be used with drugs that will easily pass through the skin, which seriously limits its usefulness.
Researchers at the University of Kentucky College of Pharmacy and the Georgia Institute of Technology have published a study, using human subjects, in which they demonstrated that patches coated with microscopic needles can painlessly deliver such compounds transdermally, including drugs, proteins, DNA and vaccines.
The study also reported that micro-needles were able to deliver therapeutic drug levels using lower doses and also reduced the production of the metabolites that may cause side-effects.
The study used the drug naltrexone, a skin-impermeable compound normally used to treat opiate and alcohol addiction. The drug was delivered by pressing and removing patches containing 50 microneedles, each of 1/40th of an inch long. A gel containing naltrexone was then applied to the skin, which was then covered by a protective dressing.
The concentration of the drug quickly reached pharmacologically active levels in the test subjects, which remained steady for at least 48 hours.
Astonishingly, 10 to 12 milligrams of the drug delivered by this method achieved the same active levels as a 50 milligram tablet, without the initial peak in bloodstream levels or rapid production of the metabolite, and therefore the side-effects, that occur with oral delivery.
Further research is being undertaken into this technique, especially in the delivery of other therapeutics such as lidocaine, insulin and flu vaccine.