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Microneedles Enhance Drug Administration With Patches

Posted: Thursday, February 14, 2008

Microneedle technology will increase the availability of medications applicable for transdermal drug delivery, a pain free and patient friendly route of drug administration. 

In what is believed to be the first peer-reviewed study of its kind involving human subjects, researchers at the University of Kentucky College of Pharmacy and the Georgia Institute of Technology have demonstrated that patches coated on one side with microscopic needles can facilitate transdermal delivery of clinically-relevant doses of a drug that normally cannot pass through the skin.

The study could help advance the use of microneedles as a painless method for delivering drugs, proteins, DNA and vaccines into the body. The research also found other advantages for the microneedles, including an ability to produce therapeutic drug levels with lower doses, and lowered production of metabolites that may cause side-effects.

"This proof-of-concept study shows that microneedles work in humans for transdermal drug delivery," said Daniel Wermeling, associate professor in the Department of Pharmacy Practice and Science at UK's College of Pharmacy. "Success with microneedles could cause us to rethink the convergence of the drug and delivery system and lead to a more integrated approach merging engineering with pharmaceutical technology."

"This study represents an important landmark in the development of microneedles into drug delivery devices suitable for use in clinical medicine," said Mark Prausnitz, a professor in the School of Chemical and Biomolecular Engineering at the Georgia Institute of Technology. "This method may be useful for a broad range of drugs that cannot normally be delivered without a hypodermic needle." Transdermal drug delivery has proven successful in a number of applications, including pain management, congestive heart failure and hormone replacement. Transdermal administration offers advantages over other delivery techniques, but existing systems can only be used for a narrow range of compounds that easily pass through the skin.

By painlessly punching a series of microscopic holes in the outer layer of skin known as the stratum corneum, microneedles promise to expand the range of drugs and vaccines that can be delivered transdermally. Until this study, however, the only published research demonstrating drug delivery using microneedles had involved studies in animals and on human cadaver skin.

Working with Prausnitz and his Georgia Tech research team, set out to determine whether microneedle patches could indeed help deliver useful amounts of drug compounds that otherwise couldn�t pass through the skin. As a test compound, they chose the drug naltrexone, a skin-impermeable compound that is used to treat opiate and alcohol addiction. Working with a small group of non-addicted human test subjects, they first prepared a section of skin on each subject�s arm by pressing and removing thumb-sized patches that contained 50 stainless steel microneedles each about 620 microns � about 1/40th of an inch � in length. Next, gel containing naltrexone was applied to the prepared area, which was then covered by a protective dressing. The concentration of the drug in each subjects� bloodstream was monitored for 72 hours. The researchers quickly saw levels of the drug reach pharmacologically active concentrations, and those levels remained steady for at least 48 hours in the six test subjects.

Beyond maintaining a steady level of the naltrexone, microneedle delivery may offer another advantage over oral administration: a reduction in the presence of compounds metabolized from the drug. The primary metabolite, known as naltrexol, is rapidly produced by the liver and intestines when the drug is administered orally, creating blood levels as much at ten times that of the parent drug � which can cause undesirable side effects. With microneedle administration, however, the levels of naltrexol stayed well below those of the naltrexone.

"There are a number of ways in which microneedles can be used," Prausnitz noted. This study addressed the simplest use of microneedles in which the needles are just inserted and removed from the skin and a drug patch applied. To understand how broadly microneedles can be used in medicine, we will also need to study delivery of other therapeutics, such as lidocaine, insulin and flu vaccine.

Source: Diabetes In Control: Reported in the journal Proceedings of the NationalAcademy of Sciences, Feb. 2008

 
 
 
 
 
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