Women may soon benefit from self-administered contraception with long-acting effects.
The most popular contraceptive methods are the pill, with 28 percent of women using it, and female sterilization, with 27 percent.
The birth control pill is effective in the short term, but more and more women are opting for long-acting methods, such as intrauterine devices and implants.
Currently, such long-acting means of contraception require a healthcare professional to administer them, but new research may bring the benefits of long-acting contraception in a much more accessible form.
Researchers led by Wei Li, a postdoctoral researcher at the Georgia Institute of Technology in Atlanta, devised an innovative technology that would deliver the contraceptive levonorgestrel through a microneedle skin patch.
Mark Prausnitz, a Regents' Professor in the School of Chemical and Biomolecular Engineering at Georgia Tech, is the corresponding author of the paper, which they have published in the journal Nature Biomedical Engineering.
Creating the patch and how it works
For their contraceptive method, Li and colleagues used microneedle skin patch technology, which scientists have already developed for administering vaccines.
The patch has drug-containing microscopic needles that break off after a person applies the patch for a few seconds. The tiny needles then remain just under the skin, releasing the drug.
Li and colleagues molded microscopic air bubbles into the top of the needles to enable them to break. The microneedles, after this modification, are strong enough for an individual to push under the skin but remain weak enough to break when they shift the patch to one side.
After the tiny needles are under the skin, they release the hormone levonorgestrel, which disrupts women's cycles. The fact that the needles consist of biodegradable polymers helps the release of the hormone.
Specifically, Li and colleagues designed the tiny needles from a mix of biodegradable polymers, such as polylactic-co-glycolic acid and polylactic acid. These acids naturally occur in the body, explain the researchers, and doctors routinely use the polymers in absorbable surgical sutures.
Study co-author Steven Schwendeman, the Ara Paul Professor, and chair of the Department of Pharmaceutical Sciences at the University of Michigan in Ann Arbor, explains the polymer selection process.
"We select polymer materials to meet specific design objectives, such as microneedle strength, biocompatibility, biodegradation and drug release time, and formulation stability," he says.
"Our team then processes the polymer into microneedles by dissolving the polymer and drug in an organic solvent, molding the shape, and then drying off the solvent to create the microneedles."
"The polymer matrix, when formed in this way, can slowly and safely release contraceptive hormone for weeks or months when placed in the body," concludes Prof. Schwendeman.
Applying the patch once a month
The researchers successfully tested the patch in rats, meaning that the concentration of levonorgestrel they delivered to the rodents via the skin patch stayed above the threshold that they knew had a contraceptive effect in humans.
However, scientists are aware of the challenges that translating these findings into humans pose.
"We do not yet know how the contraceptive microneedle patches would work in humans," Prof. Prausnitz says. "[B]ecause microneedles are, by definition, small, there are limits to how much drug can be incorporated into a microneedle patch."
However, the researcher adds, patches that could deliver the recommended dose of the drug are already available, although scientists have yet to test them.
"Because we are using a well-established contraceptive hormone, we are optimistic that the patch will be an effective contraceptive. We also expect that possible skin irritation at the site of patch application will be minimal, but these expectations need to be verified in clinical trials."
"There is a lot of interest in providing more options for long-acting contraceptives," continues Prof. Prausnitz.
"Our goal is for women to be able to self-administer long-acting contraceptives with the microneedle patch that would be applied to the skin for 5 seconds just once a month."
Prof. Mark Prausnitz