A significant number of women, especially in developing countries, need protection against more than one sexually transmitted infection (STIs), for instance HIV-1 and HSV-2, and family planning methods to prevent unwanted pregnancies. Dual protection technologies (DPTs; also known as multipurpose technologies) are designed to address two different indications with one product. Examples of DPTs are vaginal products capable of preventing transmission of HIV-1 in women while simultaneously providing contraceptive properties and a vaginal product capable of reducing HIV-1 transmission while preventing transmission of a second STI. DPTs can be categorized into three main approaches: 1) physical barriers, 2) chemical barriers, and 3) a combination of physical and chemical barriers. Examples of physical barriers are male and female condoms, diaphragms and cervical caps. Chemical barriers include use of a single drug with two mechanisms of action (viz., dual-activity compounds with microbicidal and contraceptive properties or activity against HIV-1 and a second STI pathogen such as HSV-2) or a combination of two drugs each targeted against separate mechanisms for achieving contraception and inhibition of HIV-1. Combinations of chemical and physical barriers are based on physical barriers such as a diaphragm along with a microbicide. Examples of each approach and current prototypes (such as vaginal gels and intravaginal rings) under development are described in this paper. Challenges facing development and regulatory approval of DPTs are also reviewed. This article forms part of a special supplement on a presentation covering DPTs, based on the symposium "Trends in Microbicide Formulations", held on 25 and 26 January 2010, Arlington, VA.
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