Thanks to an innovative "depot” injection approach from a team at MIT, long-lasting shots could become a lot less painful. Involving the injection of tiny, drug-delivering crystals suspended within a solvent, the team’s method could deliver drugs with thinner needles, fewer injections, and a lot less pain overall.
Describing the approach in a study in Nature Chemical Engineering, the team says that the method could work with contraceptives and other drugs that are taken consistently over time.
“We showed that we can have very controlled, sustained delivery, likely for multiple months and even years through a small needle,” said Giovanni Traverso, the senior study author and a mechanical engineering professor at MIT, according to a press release.
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Drug Delivery in Slow, Steady Shots
A depot injection is a type of shot that releases a drug slowly and steadily over time. While other depot injections have been developed to solidify into drug deposits beneath the skin, the polymers that are added to these shots to allow them to solidify add to their bulk, comprising around 23 percent to 98 percent of their overall weight. This requires them to be injected through thicker needles that are difficult for patients to tolerate.
To develop a better alternative, the MIT team devised a shot that could be delivered through a thinner needle and still last for at least three months. Working with a contraceptive drug that transforms into crystals suspended in a solvent, the shot could solidify into a drug deposit beneath the skin without the need of large amounts of polymers, allowing it to be injected through thinner, more tolerable needles.
The method could expand patients’ options for contraception, providing them with “a lot of different formats for contraception that are easy to administer,” said Vivian Feig, a lead study author and a former MIT postdoc, according to the release.
Not only that; the approach could also provide patients with more drug delivery options for other drugs that are administered over time, including long-lasting drugs for HIV and tuberculosis.
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Developing Drug Delivery Options
According to the team, the trick to the shot was the combination of the crystalline contraceptive levonorgestrel and the solvent benzyl benzoate. By adding tiny crystals of this contraceptive to this solvent, the team created a shot that could assemble into a solid drug deposit after injection without large additions of polymers.
“The solvent is critical because it allows you to inject the fluid through a small needle, but once in place, the crystals self-assemble into a drug depot,” Traverso said in the release.
By adjusting the density of the deposit with only a small addition of polymers (no more than 1.6 percent of the shot’s overall weight), the researchers found that they could control the rate of the drug’s release throughout the body, still without requiring a thicker needle.
“This demonstrates the tunability of our system, which can be engineered to accommodate a broader range of contraceptive needs as well as tailored dosing regimens for other therapeutic applications,” said Sanghyun Park, another lead study author and a MIT graduate student, in the release.
Though the approach has not been tested in humans, studies in rats show that the drug deposits stick around for at least three months beneath the skin. At that point, around 85 percent of the drug is still sitting in the depots — an amount that indicates that these deposits “could last for more than a year,” Park said in the release.
Additional animal studies are already underway to determine whether the method is fit for human testing, whether as a delivery method for contraceptives or for other long-lasting drugs.
“Is it contraception? Is it others? These are some of the things that we’re starting to look into as part of the next steps toward translation to humans,” Traverso added in the release.
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Nature Chemical Engineering. Self-Aggregating Long-Acting Injectable Microcrystals
Sam Walters is a journalist covering archaeology, paleontology, ecology, and evolution for Discover, along with an assortment of other topics. Before joining the Discover team as an assistant editor in 2022, Sam studied journalism at Northwestern University in Evanston, Illinois.
