A new long-acting contraceptive designed to be self-administered by women may provide a new family planning option, particularly in developing nations where access to healthcare can be limited, a recent study suggests. The contraceptive would be delivered using microneedle skin patch technology originally developed for the painless administration of vaccines.
Long-acting contraceptives now available provide the highest level of effectiveness, but usually require a healthcare professional to inject a drug or implant a device. Short-acting techniques, on the other hand, require frequent compliance by users and therefore are often not as effective. In animal testing, an experimental microneedle contraceptive patch provided a therapeutic level of contraceptive hormone for more than a month with a single application to the skin.
When the patch is applied for several seconds, the microscopic needles break off and remain under the surface of the skin, where biodegradable polymers slowly release the contraceptive drug levonorgestrel over time. Originally designed for use in areas of the world with limited access to health care, the microneedle contraceptive could potentially provide a new family planning alternative to a broader population. The research was reported in the journal Nature Biomedical Engineering.
"There is a lot of interest in providing more options for long-acting contraceptives," said the paper's corresponding author. "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 five seconds just once a month."
Long-acting contraceptives are now available in formats such as patches that must be worn continuously, intrauterine devices (IUDs) that must be placed by trained healthcare professionals, and drugs injected with hypodermic needles. If the microneedle contraceptive patch is ultimately approved for use, it could become the first self-administered, long-acting contraceptive that does not involve a conventional needle injection. Like other long-acting contraceptive techniques, the microneedle contraceptive patch would disrupt the menstrual cycles of women using it.
Because the tiny needles must remain in the skin for the time-release of the hormone, researchers developed a mechanical technique that would allow the drug-containing microneedles to break free from the patch's backing material. To accomplish that, the researchers molded tiny air bubbles into the top of the microneedles, creating a structural weakness. The resulting microneedles are strong enough to be pressed into the skin, but when the patch is then shifted to one side, the shear force breaks off the tiny structures in the skin. The patch backing can then be discarded.
Experimental patches designed to deliver a sufficient amount of the hormone for humans have been developed, but not yet tested, noted the senior author. Researchers are also studying whether a single patch could carry enough hormone to provide contraception for as long as six months.
"We select polymer materials to meet specific design objectives such as microneedle strength, biocompatibility, biodegradation and drug release time, and formulation stability," the author explained. "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."
Testing with rats evaluated only the blood levels of the hormone and did not attempt to determine whether it could prevent pregnancy. "The goal was to show that we could enable the concentration of the levonorgestrel to stay above levels that are known to cause contraception in humans," the senior author explained.
In developing the experimental contraceptive microneedle patch, the researchers leveraged earlier work on dissolving microneedle patches designed to carry vaccines into the body. A Phase I clinical trial of influenza vaccination using rapidly dissolving microneedles has been conducted in collaboration with Emory University.
That study suggested that the microneedle patches could be safely used to administer the vaccine. Because the microneedles are so small, they enter only the upper layers of the skin and were not perceived as painful by study participants.
"We do not yet know how the contraceptive microneedle patches would work in humans," the senior author said. "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."
The contraceptive patches tested on the animals contained 100 microneedles. To deliver an adequate dose of levonorgestrel to a human will require a larger patch, which has been fabricated, but not yet tested. The researchers would like to develop a patch that could be applied once every six months.
Microneedle, self administered contraceptive patch for the sustained release
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