Microbicides For Sexually Transmitted Diseases - Formulations

Formulations

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.

Substantial numbers of men who have sex with men in developed countries use lubricants containing nonoxynol-9. This suggests that they might be receptive to the concept of using topical rectal microbicides if such products were to become commercially available. However, the development of rectal microbicides is not as advanced as that of vaginal microbicides. One reason for this is that the rectum has a thinner epithelium, greater surface area and lower degree of elasticity than that of the vagina. Due to these factors, a microbicidal preparation that is effective when applied vaginally might have a different degree of effectiveness when applied rectally. In January 2010, the National Institutes of Health awarded two grants totaling $17.5 million to the University of Pittsburgh to fund research into rectal microbicides. That research will include investigations into product acceptability of rectal microbicides with homosexual men ages 18 to 30 years old.

Ultimately, successful topical microbicides might simultaneously employ multiple modes of action. In fact, long-acting formulations such as vaginal rings could provide the technology needed to deliver multiple active ingredients with different mechanisms of action.