Monthly oral contraceptive capsule shown to work in pigs

An oral contraceptive capsule may only need to be taken once a month. In tests in pigs, the capsule slowly released a contraceptive into the stomach that then persisted in the blood for weeks.

“This is the first example that I’m aware of a capsule that can deliver a drug over the course of a month,” says Giovanni Traverso at the Massachusetts Institute of Technology, part of the team that developed the capsule.

The team designed the capsule’s drug delivery system so that it would stick around in the stomach. Within the capsule is a structure made up of six arms attached to a central body. Each arm is loaded with the progestogen contraceptive levonorgestrel.

While inside the capsule the structure is folded up, but once the capsule reaches the stomach it starts to degrade. This releases the structure, allowing the arms to unfold and create a star that opens to such a size that it cannot fit through the sphincter that controls the exit of the stomach. Over the next few weeks, the hormone is gradually released, before the arms eventually fall off and the pieces pass through the body, says Traverso.

So far, Traverso and his colleagues have only tested their contraceptive in pigs. Three animals given the capsule had similar blood levels of the contraceptive to five female pigs that were given the daily version of the oral contraceptive, although these levels did drop over the course of a month.

Discreet contraceptive

The researchers plan to incorporate oestrogen along with progestogen before they trial the capsule in people as this is the more common format for long-acting contraceptives, says Traverso. He hopes to start human trials within the next five years. He imagines the once-a-month contraceptive being especially useful in low-to-middle income countries.

“There are over 200 million women of reproductive age in developing regions who want to avoid pregnancy but are not using any modern contraceptives,” says Traverso. “The goal here was to develop a discreet, non-invasive system that can provide long-acting oral contraception.” His colleagues are currently researching the demand for such contraceptives in these regions.

“It’s an exciting idea,” says Stephanie Page at the University of Washington School of Medicine in Seattle. Long-acting contraceptives tend to be more effective than daily pills, she says. Taking a pill once a month might be more discreet than visiting a clinic or having a visible implant, and so might appeal to women who want to use contraceptives against the wishes of their partners.

“Anything that increases the diversity of methods available to people who want to use contraception is a plus,” says Page. But she cautions that there is a long way to go before the results can be translated to women. And the level of drug in a woman’s blood is likely to be influenced by her body size, what she has eaten and any other medications she is taking. “The variability in drug levels in this sort of system could take a long time to sort out,” she says.

In the meantime, Traverso and his colleagues are investigating how their slow-release system could also be used to deliver other drugs over long periods of time. The team is researching ways to treat HIV, Alzheimer’s disease and malaria using a similar capsule, he says.