Convenient monthly contraceptive pill may soon replace daily doses

USA: A once-a-month oral contraceptive could soon replace daily doses. This will reduce the risk of having unintended pregnancies even when one forgets to take the daily dose of their birth-control pill. These are the findings from a recent study published in the Science Translational Medicine journal.

The pills, being developed by MIT researchers, could have a significant impact on the health of women and their families.

Female contraceptive provides women with a means to manage their fertility, spacing pregnancies, controlling family size and maintaining health. There are several methods for hormonal contraception including subcutaneous implants, intrauterine devices, vaginal rings, transdermal patches, injectables, and oral pills.

Oral contraceptives are one of the most popular forms of birth control that have the shortest duration and need to be taken daily. They are popular because of their ease of use, an opportunity for self-administration and rapid resumption of fertility after their discontinuation. However, their effectiveness is compromised owing to a lack of patient adherence. A multinational survey has revealed that over a 3-month interval, nearly 40 to 50% of women missed at least one dose and a similar percentage of women took the medication at the wrong time.

"Patient adherence to medications can be increased by reducing dosing frequency. Adherence to monthly therapies is greater than adherence to weekly and daily therapies. Hence, an orally administered long-acting contraceptive could improve patient adherence in the population that prefers pills. Unfortunately, orally administered drug delivery systems have a short gastrointestinal transit time, providing a limited interval for drug delivery," wrote the authors.

To address this issue, Ameya R. Kirtane, Massachusetts Institute of Technology, Cambridge, MA, USA, and colleagues have developed a gastric resident dosage form that can be placed in a gelatin capsule to enable oral administration. This dosage form, once ingested, expands and resides in the stomach for extended periods, providing drug release for 3 weeks with a hormone-free period, which would be associated with the recognized breakthrough bleeding that would also serve as a reminder for the next monthly dose.

To make their new contraceptive pill last for three to four weeks, the researchers had to incorporate stronger materials than those used in the earlier versions, which could survive in the harsh environment of the stomach for up to two weeks. The researchers tested materials by soaking them in simulated gastric fluid, which is very acidic, and found that two types of polyurethane worked best for the arms and the central core of the star.

The researchers loaded the contraceptive drug levonorgestrel into the arms of the device and found that by changing the concentrations of the polymers that they mix with the drug, they can control the rate at which it is released. Once the capsule reaches the stomach it expands and becomes lodged in place.

In a study of pigs, the researchers found that the capsules could release the drug at a fairly constant rate for up to four weeks. The concentration of the drug found in the pigs' bloodstream was similar to the amount that would be present after ingesting daily levonorgestrel tablets. However, the capsules maintained these drug levels for nearly a month, while the tablets last for only a day.

For use in humans, the capsule would be designed to break down after three or four weeks and exit the body through the digestive tract. The researchers are working on several possible ways to trigger the arms to break off, including through changes in pH, changes in temperature, or exposure to certain chemicals.

The study, "A once-a-month oral contraceptive," is published in the journal Science Translational Medicine.

DOI: 10.1126/scitranslmed.aay2602