Cellulose sulfate

Microbicides for sexually transmitted diseases are pharmacologic agents and chemical substances that are capable of killing or destroying certain microorganisms that commonly cause human infection (for example, the human immunodeficiency virus).Detergent and surfactant microbicides such as nonoxynol-9, sodium dodecyl sulfate and Savvy (1.0% C31G), act by disrupting the viral envelope, capsid or lipid membrane of microorganisms. Since detergent microbicides also kill host cells and impair the barrier function of healthy mucosal surfaces, they are less desirable than other agents. Additionally, clinical trials have not demonstrated these agents to be effective at preventing HIV transmission. Consequently, laboratory and clinical trials testing this class of products as microbicides have largely been discontinued.Most of the first generation microbicides were formulated as semi-solid systems, such as gels, tablets, films, or creams, and were designed to be applied to the vagina before every act of intercourse. However, vaginal rings have the potential to provide long-term controlled release of microbicide drugs. Long-acting formulations, like vaginal rings, are potentially advantageous since they could be easy to use, requiring replacement only once a month. This ease of use could prove very important to make sure that products are used properly. In 2010, the International Partnership for Microbicides began the first study in Africa to test the safety and acceptability of a vaginal ring containing dapivirine. Drugs might also be administered systemically through injectable or oral formulations known as PrEP. Injectable formulations may be desirable since they could be administered infrequently, possibly once a month. It is likely, however, that such products would need to be monitored closely and would be available only through prescription. This approach also carries the risk of emergence of ARV-resistant strains of HIV.A major breakthrough in microbicide research, announced in July 2010, reported that an ARV-based microbicide gel could partially prevent HIV. A trial led by the Centre for the AIDS Programme of Research in South Africa (CAPRISA), conducted in South Africa, demonstrated that the ARV tenofovir, when used in a vaginal gel, was 39% effective at preventing HIV transmission from men to women during sex.Efforts are underway to develop safe and effective topical microbicides. Several different gel formulations are currently undergoing testing in phase III clinical efficacy trials, and about two dozen other products are in various phases of development. Results from CAPRISA 004, while promising, may need to be confirmed by other clinical trials before the microbicide tenofovir gel is made available to the public. This decision rests with regulators, particularly in South Africa. In 2013, the VOICE study (MTN 003), another large-scale trial, is scheduled to release results. VOICE is evaluating three different strategies to prevent HIV in women: one ARV-based microbicide and two regimens consisting of oral ARVs on a daily basis. The VOICE trial is testing 1% tenofovir vaginal gel in a once-daily formulation. It is not known at this time if VOICE will be considered a confirmatory trial for CAPRISA 004, which used a different dosing strategy. Products known as Pre-Exposure Prophylaxis, or PrEP, are also being tested at various stages of the development process. These products, administered orally or via injection, would contain ARVs to protect HIV-negative people from becoming infected. Individuals would receive ARVs before they were exposed to HIV, with the goal of lowering their risk or preventing infection. One of the potential advantages of PrEP is that an individual could use it autonomously (without the need to negotiate with a partner), and it is not dependent on the time of sex. It is hoped that those unable to negotiate condom use with their sexual partners would be able to reduce their risk of HIV infection with the use of an oral (or injectable) prophylactic drug. Current PrEP candidates in development include tenofovir and Truvada (a combination of two ARV compounds, tenofovir and emtricitabine). One potential risk of the PrEP approach is that drugs present in systemic circulation might, over time, create ARV-resistant HIV strains.Condoms are an effective method for blocking the transmission of most sexually transmitted diseases (with HPV a notable exception). However, a variety of social factors (including, but not limited to, the sexual disempowerment of women in many cultures) limit the feasibility of condom use. Thus, topical microbicides might provide a useful woman-initiated alternative to condoms.