New intravaginal ring protects against HIV as well as unwanted pregnancy
A Northwestern University biomedical engineer has designed a first-of-its-kind intravaginal ring that reliably delivers an antiretroviral drug and a contraceptive for months.
Patrick Kiser's one ring delivers two drugs that do three important things: the device is designed to protect against HIV and herpes as well as unwanted pregnancy. It will be the first device with the potential to offer this protection to be tested in women.
The easy-to-use ring delivers controlled doses of tenofovir (a common antiretroviral drug) and levonorgestrel (a contraceptive) for 90 days. The rings are being manufactured now, and the device soon will undergo its first test in women.
According to the World Health Organization, 35 million people around the world live with HIV, and 222 million women would like to delay or stop childbearing but are not using any method of contraception.
"I suspect women will use the ring primarily for contraception, but they also will benefit from protection against sexually transmitted diseases," Kiser, an expert in intravaginal drug delivery, said.
"And for women in the developing world in particular, unwanted pregnancy can have significant health, economic and cultural consequences. We want to motivate women to use this ring," he said.
The ring, 5.5 centimeters in diameter, is simple yet complex. Kiser and his colleagues worked painstakingly for five years, engineering the three materials that make up the ring and optimizing the device to reliably deliver fixed and efficacious doses of two medicines over a long period of time.
The ring is easily inserted in the vagina and stays in place for three months. And because the tenofovir is delivered at the site of transmission, the ring -- known as the tenofovir levonorgestrel IVR -- utilizes a smaller dose than pills. The levonorgestrel released by the ring is the same drug as that used in certain contraceptive pills and in an intrauterine device.
Previous studies have demonstrated that antiretroviral drugs can prevent HIV infection, but existing methods for delivering the drug fall short. Pills must be taken daily and require high doses; some women may prefer a longer-lasting method, such as the ring, versus methods used at the time of sex, such as a gel.
Kiser's combination ring promises much more. The strength of the device stems from its unique polymer construction: its elastomer swells in the presence of fluid (such as that found in the human body), delivering up to 100 times more of the tenofovir than current intravaginal ring technology, which have release rates that decline over time.
The antiretroviral drug section of the ring is made of one kind of polyurethane, and the contraceptive section of the ring is made of another polyurethane. Each material needed to be engineered with the correct diffusion rates, so the encapsulated drug is released into the body at the desired rate, providing the correct dose.
A third polyurethane material between the two sections keeps the drugs separate. All the parts are welded together to complete the ring.
The research is published by PLOS ONE, a peer-reviewed, open-access online journal.
(Posted on 06-03-2014)