ORF 13904, a new long-acting vaginal contraceptive.

A sulfonated polystyrene polymer, ORF 13904, was discovered in our laboratory to be a highly effective vaginal contraceptive in the rabbit model and to possess a unique mode of action. It was found to be non-spermicidal even at high concentrations, yet it greatly impeded sperm penetration of cervical mucus in vitro. When a gel formulation containing 5% ORF 13904 was administered to rabbits intravaginally, the mean number of fetal implants was reduced dramatically even when coitus was delayed for up to 8 hours or when multiple matings at different time intervals were permitted. The non-spermicidal qualities and extended duration of action of this compound represent major breakthroughs in the development of vaginal contraceptives.