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A nurse wielding a hypodermic needle is unlikely to conjure up calm thoughts, let alone inspire you to go solo and administer the injection yourself. But a new patch lined with short needles, each the width of just a few strands of hair, may soon grant squeamish patients a reprieve as well as a relatively simple opportunity to take matters into their own hands. The innovation could eliminate the pain and fear of getting shots, researchers say, and it could also make future vaccines and medical treatments safer, more effective and easier to self-administer.
"You don't need a big needle," says Mark Prausnitz, an expert in drug delivery at the Georgia Institute of Technology who presented preliminary research on the microneedle patch this week at the national meeting of the American Chemical Society (ACS). "A very small needle will do."
In looking at the skin's anatomy, Prausnitz and his Georgia Tech team determined that a needle shorter and thinner than those traditionally used could still gain access to the body—penetrating just far enough into the thin barrier of the skin to deliver medicine into a rich array of capillaries. In fact, that depth may be even more optimal in some cases than the subcutaneous destination of the hypodermic needle. (The big needle, however, is still necessary for direct intravenous injections.) The length is the critical part, Prausnitz notes, but the needles' thinness minimizes pain and keeps it from "looking scary."
There are many ways to administer a medication, probably the easiest of which is popping a pill. Unfortunately, many drugs and vaccines simply cannot be given orally, as the gastrointestinal tract destroys any useful dose. (The measles vaccine may be one of the exceptions: an inhalant powder was revealed this week at the same ACS meeting.) And, despite the benefits of the transdermal patch, it is rare for a medication to cross the human skin barrier as it is actually designed to keep most things out. The obvious alternative for the past century and a half has been a hypodermic needle. But it, too, has its problems—and not just in terms of pain. "Handing somebody a bottle of pills versus a pile of needles and syringes," Prausnitz says, "leads to two totally different prospects [in terms of compliance]."
Another option was needed. Prausnitz and his colleagues' answer was a hybrid of the ease and convenience of the transdermal patch and the delivery power of the needle. "It's as friendly and painless as a pill," he says, "but its able to cross the skin and get into the body."
The biggest benefit of the new approach may be the ease with which people could self-administer drugs or vaccines. Preliminary work with diabetics has found the patch can deliver insulin successfully and with less pain than a hypodermic. The method could also increase the number of people who actually get vaccines, Prausnitz says. "Instead of needing to go to the doctor, you could just stop by a pharmacy and pick up a patch," he says, noting that this could be especially helpful in the case of the current H1N1 "swine" flu outbreak, or any other future pandemic, where vaccines need to be delivered quickly. Using only doctor-administered injections "could take months before the whole country would be vaccinated," he says. "But if you empower the patient, the U.S. Postal Service could deliver vaccines to everyone's home and the whole country could be vaccinated in a matter of days."
Prausnitz and his team collaborated with researchers at Emory University to test the effectiveness of a flu vaccine administered via the patch compared with conventional injections in mice. The team found the microneedles provided an equal, if not slightly more protective, immune response. The first human trials of the flu vaccine patch are expected to begin in 2010, but it will likely be at least a couple more years beyond that before it is in widespread use.
Although Prausnitz's team is not the only lab working on the microneedle approach, he thinks it is the first to apply the technology to the eye. For those suffering from macular degeneration—the leading cause of blindness in the U.S.—monthly injections into the back of the eye can be burdensome. So a needle that pricks just into the surface of the eye would be a welcome relief. Once the patch is in place, drugs can flow backward, between tissue layers in the white of the eye until they reach the target on the other side. This may be one case where the best route between two points is not a straight line.
