Intra vaginal rings have been made for many years in various polymer materials such as EVA, LSR and polyurethane elastomers and thermoplastics, to slowly release active pharmaceutical ingredients. This has been in the form of polymer “reservoir rings” (“core”) with a hollow core containing dissolved APIs, “sandwich” (“shell”) ring versions or solid “matrix” rings with one or more APIs incorporated within the polymer matrix.
Researchers at Queens University Belfast in Northern Ireland have observed that reservoir and sandwich rings involve complex production but release API at a low but constant rate, while matrix rings are easier to produce, but with a tendency of some API level depletion with time in the outer part of the material.
Results of clinical trials published in February 2016 by the non-profit organization IPM International Partnership for Microbicides in Silver Spring, Md., and MTN Microbiocide Trials Network found an LSR matrix ring containing 25 milligrams of the antiretroviral non-nucleoside reverse transcriptase inhibitor drug Dapivirine had reduced HIV infection rates by respectively 31 and 27 percent when used for 28 days.
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