A novel intravaginal ring implanted with anti-retroviral drug tablets, or pods, maintained steady state drug levels in the vaginal tissues, the key anatomic compartment for preventing sexual HIV transmission, says a study.
The ring, designed to prevent transmission of HIV, was tested in pig-tailed macaque monkeys, and demonstrated sustained and controlled drug release and safety over 28 days, the study said.
As people often fail to take their medications as prescribed, the ring's topical drug delivery has critical advantages over oral therapy, the researchers noted.
"The ring maintained steady state drug levels in the vaginal tissues, the key anatomic compartment for preventing sexual HIV transmission, and eliminated the concentration troughs encountered with oral medications," said Marc Baum from Oak Crest Institute of Science, Pasadena in the US.
"Issues such as adherence to a regular dosing schedule are significantly reduced by continuous release of the drugs into the vaginal mucosa independently of coitus and daily dosing," he added.
One of the two drug combinations tested in the ring had been shown in three clinical trials to prevent HIV "some of the time" when taken orally, and is the only product approved by the US Food and Drug Administration (FDA) for HIV prophylaxis.
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The ring is a simple, unmedicated, impermeable elastomer scaffold on which the investigators implanted polymer-coated drug tablets, each containing a different drug.
These deliver the drug directly to the vaginal mucosa, via channels in the elastomer ring, which exposes the pods to vaginal fluids.
The study appeared in the journal Antimicrobial Agents and Chemotherapy.