A contraceptive implant is a thin and flexible rod that sits under the skin and releases contraceptive drugs into the body for years. While it’s one of the most effective forms of contraceptives and avoids the inconvenience of having to take a pill every day, the implant requires minor surgery, which can limit accessibility. To make life a bit easier, researchers are creating a self-assembling contraceptive implant the components of which women could self-administer with a single injection.
A team of researchers has developed the technology for self-injectable contraceptive shots that work similarly to contraceptive implants. As detailed in a study published Monday in the journal Nature Chemical Engineering, the shots would result in a highly effective and long-term contraceptive method more accessible to women who lack easy access to medical infrastructure. Additionally, the design could be used to administer other long-term medications, such as those for HIV.
The new approach delivers the contraceptive hormonal medication levonorgestrel via what the researchers call “Self-assembling Long-acting Injectable Microcrystals” (SLIM). Once injected into the body, the tiny crystals assemble into an implant, or a drug “depot,” that releases levonorgestrel as it erodes over months or years.
“The overarching goal is to give women access to a lot of different formats for contraception that are easy to administer, compatible with being used in the developing world, and have a range of different timeframes of durations of action,” Vivian Feig, a mechanical engineer at Stanford University and co-author on the study, said in a Massachusetts Institute of Technology (MIT) statement.
Traditional birth control shots already exist and are more accessible than the contraceptive implant because patients can give themselves the shots without having to visit a hospital or medical clinic. However, they are slightly less effective than the implant and are not long-lasting, so they must be administered every three months.
The researchers’ new contraceptive design joins the accessibility of self-administered shots with the long-term efficacy of an implant. The challenge of self-administering technologies similar to SLIM, however, has been the large (and hence painful) needle size necessary to inject the medication. By contrast, the team’s formula—tiny crystals and a solvent (in this case a liquid compound called benzyl benzoate)—allows for the use of much smaller needles.
“Needle size and liquid viscosity are crucial considerations for commercial translation of injectables,” said Giovanni Traverso, senior author of the study and a gastroenterologist at MIT and Brigham and Women’s Hospital, in a Mass General Brigham statement. “Our engineering challenge was finding a way to maximize comfort for patients by using smaller needles, which cause less bruising or bleeding, and to make the viscosity low enough for easy application with the syringe by hand.”
Furthermore, Traverso and his colleagues can modify the mixture to “modulate the drug release rate, extending its duration while maintaining injectability,” MIT graduate student Sanghyun Park explained in the MIT statement. “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.”
While SLIM hasn’t gone through clinical trials yet, the development of the technology in preclinical models paves the way for more convenient and effective future long-term medications.
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