Nonoxynol 9 is an organic compound that serves as the active ingredient in a wide range of contraceptive products. Among these are diaphragms, cervical cap jelly, spermicial foam, contraceptive sponges, and spemicidal suppositories. It has a failure rate of between 10 - 20%.
Some condom lubricants contain nonoxynol 9. Its stated purpose is to serve as backup method in preventing preganancy. In theory, it is a microbicide and thus can offer some protection against STIs should the condom break. However, no scientific evidence has been published to support these claims.