In the not so distant future, drugs given by injection could be less painful and less frequent.

Many medications, like contraceptives and treatments for chronic conditions, require regular and painful injections.

But MIT’s Bill Gates-funded injection could offer years of birth control with just one shot.

Interestng engineering reports: MIT engineers have developed a new, less painful drug delivery system using injectable crystal suspensions. These crystals form a long-lasting “depot” under the skin, releasing medication over months or years, and reducing the need for frequent injections.

“We showed that we can have very controlled, sustained delivery, likely for multiple months and even years through a small needle,” said Giovanni Traverso, an associate professor of mechanical engineering at MIT.

Drug depot under skin

This research focuses on developing improved contraceptive options for women, especially in developing nations. 

Some injectable suspensions exist, but they are short-acting. Other long-lasting injectable depots require high concentrations of polymers, making them difficult to inject. This new development aims to address these limitations.

The objective was to produce a drug delivery system that could be administered via a thin needle and provide sustained release for six months to two years.

For the development, the team used levonorgestrel, a crystal-forming contraceptive. 

It was found that suspending it in biocompatible benzyl benzoate solvent allowed the crystals to form a compact, long-lasting implant after injection. This acted like a self-assembling drug depot under the skin.

The researchers discovered that the solvent’s inability to mix with bodily fluids is key for the drug crystals to clump together and form a long-lasting drug reservoir (depot) beneath the skin post-injection.

This method enables easier injection through a thin needle.

“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 added.