Intravaginal Ring Could be Used in New Approach to AIDS Prevention

HARROGATE, United Kingdom -- An intravaginal ring that releases antibiotic has been developed by scientists at Queen's University Belfast. The ring will initially be used to treat a common vaginal infection but it also has potential use as part of a strategy to prevent HIV infection, the British Pharmaceutical Conference heard this week.

The Belfast researchers have a longstanding research program into the development of intravaginal rings as drug delivery systems. The rings are made of silicone rubber and are positioned high in the vagina. They can be formulated to release drug over weeks or months, for either local or systemic delivery.

The new ring is designed to treat bacterial vaginosis, a common vaginal infection. The antibiotic (metronidazole) diffuses through the silicone and dissolves in the vaginal fluid.

Researcher Karl Malcolm reported in vitro studies which showed that metronidazole was released from the ring over 14 days and was effective in killing Gardnerella vaginalis, one of the causative organisms associated with bacterial vaginosis. He explained, "Metronidazole is released in steadily decreasing amounts over the treatment period. The release profile mimics the reduction in bacterial population and avoids unnecessary exposure to drug."

At present, bacterial vaginosis is often treated with metronidazole given orally or by vaginal gel. Malcolm commented, "Oral administration is associated with a range of side effects, including nausea and vomiting, while the current vaginal gel formulations, like all vaginal gels, are messy, difficult to apply and are poorly retained within the vagina." The Belfast researchers believe that the ability to deliver controlled amounts of drug vaginally could provide significant advantages for many patients.

A ring releasing metronidazole, either alone or in conjunction with an antiretroviral agent, could also have considerable potential in preventing HIV infection.

Malcolm said, "Bacterial vaginosis, and other sexually transmitted diseases, have been widely implicated in an increased risk of sexually transmitted HIV infection. Wheareas HIV does not survive long in the normal acidic environment of the vagina, it thrives at the elevated pH associated with bacterial vaginosis infection. Simply treating existing, and in many cases asymptomatic, vaginal infections could have a massive impact on sexually transmitted HIV statistics. The chance of an effective HIV vaccine being developed and marketed within the next 10 years is slim to say the least. Of course, it is imperative that the vaccine research continues, but it is equally imperative that alternative preventative strategies are pursued. Vaginal microbicides are the obvious alternative."

Source: British Pharmaceutical Conference