An intravaginal ring that works as a contraceptive while also killing HIV and herpes has been announced in PLOS One. Although it does not provide protection against the broad spectrum of sexual transmitted infections that condoms offer, a single device is expected to retain its effectiveness for three months.
The ring is inserted into the vagina and releases tenofovir, an antiretroviral that kills HIV and herpes, and levonorgestrel, a contraceptive. "A lot of engineering has gone into developing the ring," said Dr Patrick Kiser of Northwestern University, senior author of the paper. "It represents two Ph.D. theses—one Ph.D. for the larger section containing the antiretroviral drug and another Ph.D. for the smaller section containing the contraceptive."
"The differences between the two drugs are huge, which presented us with a design challenge," Kiser said. "Tenofovir is highly water soluble while levonorgestrel is highly water insoluble. And the daily dose is different: the ring delivers about 10 milligrams of tenofovir and only 10 micrograms of levonorgestrel. Our scientific hurdle was finding a way to manufacture a dual-purpose ring that got the device into the clinic."
Currently known as the tenofovir levonorgesterel IVR, the ring has the advantage of releasing smaller amounts of the drugs than oral equivalents, as the dose is at the site of transmission. The elastomer from which it is made swells in the presence of fluid and releases 100 times as much tenofovir as previous intravaginal rings.
Impressive as the engineering has been to get to this point, the device is yet to be tested in humans, although it has shown to work in rabbits. The history of contraception is littered with brilliant ideas that never proved popular with users. The female condom, for example, was hailed as the solution to the AIDS crisis in the developing world, but proved far less popular than expected, although it now may be experiencing a revival.
Sexual health experts have pointed to challenges a contraceptive of this sort must face beyond mastering slow chemical release. "I'm particularly concerned about patient education, practicality and cost," said Karyn Fulcher of sex education organisation Scarleteen.
By offering something that only has to be replaced every three months, the researchers hope to resolve many of the problems with pills that must be taken daily, or condoms that need to be used just when people are least likely to be thinking clearly. It would be particularly suited to locations where access to contraception is unreliable. The researchers simulated storage at 37ºC for five years, but the challenges of distribution in tropical conditions are substantial.
"I suspect women will use the ring primarily for contraception, but they also will benefit from protection against sexually transmitted diseases," said Kiser, an expert in intravaginal drug delivery. "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."