Painless microneedle patch provides month-long contraception

Contraceptives are rarely convenient – implanted devices are invasive, and you have to remember to take the pill every day. Now a team led by researchers at Georgia Tech are developing a painless, contraceptive microneedle patch that women can apply themselves in five seconds, and only needs to be done once a month.

Microneedle patches have been doing the rounds for the better part of a decade now. When these patches are applied to the skin, they deliver drugs through an array of tiny needles that either dissolve or break off under the skin. In the past, scientists have tested using them to deliver antibiotics, flu vaccines, insulin, skin cancer drugs, blood thinners (for fighting blood clots), and even drugs to melt fat.

So it makes sense that contraceptives would join that list. Microneedle patches have a wide range of advantages: people can administer them at home without needing medical supervision, and because the needles end up in the skin, there's no hazardous sharps waste. They're also relatively inexpensive and don't need to be refrigerated, making them easier to store and transport.

In this case, the patch delivers a drug called levonorgestrel, which is the active ingredient in the "morning after" pill. While it works in the same general way as the other patches, the Georgia Tech researchers developed a new design that would let it slowly release the payload over a month.

Tiny air bubbles are molded into the tops of the microneedles, so that when the patch is shifted sideways the needles break off easily. The microneedles are made of the active ingredient levonorgestrel, mixed with polymers that safely break down in the body, releasing the drug for weeks at a time, and potentially longer.

Testing the patch on rats, the team found that 100 microneedles were enough to raise the levels of levonorgestrel in their bloodstream high enough to have a contraceptive effect. One application was enough to keep them that high for over a month. That said, for this experiment the researchers didn't follow through to check if it would prevent pregnancy, but prior knowledge of the hormone says it should in those amounts.

The team has already developed a larger patch for human use, which is due to be tested soon. A future version may even be able to carry enough of the drug to last six months, but more work is needed to iron out the kinks.

"We do not yet know how the contraceptive microneedle patches would work in humans," says Mark Prausnitz, corresponding author of the study. "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 research was published in the journal Nature Biomedical Engineering.

Source: Georgia Tech via Eurekalert