Advances in microbicide vaginal rings.

Vaginal ring devices capable of providing sustained/controlled release of incorporated actives are already marketed for steroidal contraception and estrogen replacement therapy. In recent years, there has been considerable interest in developing similar ring devices for the administration of microbicidal compounds to prevent vaginal HIV transmission. Intended to be worn continuously, such coitally independent microbicide rings are being developed to maintain effective vaginal microbicide concentrations over many weeks or months, thereby overcoming issues around timing of product application, user compliance and acceptability associated with more conventional semi-solid formulations. In this article, an overview of vaginal ring technologies is presented, followed by a review of recent advances and issues pertaining to their application for the delivery of HIV microbicides. This article forms part of a special supplement on presentations covering intravaginal rings, based on the symposium "Trends in Microbicide Formulations", held on 25 and 26 January 2010, Arlington, VA.