Foam, suppositories, the sponge, creams and jellies, and VCF all contain a spermicide, a chemical that kills sperm. When foam is inserted with the applicator, it rapidly covers the vaginal walls and the cervical os, or opening to the uterus (see Figure 10.5). Con­traceptive vaginal suppositories take about 20 minutes to dissolve and cover the walls. One brand of suppository, Encare, effervesces and creates foam inside the vagina; other brands melt. Once VCF is inserted into the vagina, next to the cervix, it dissolves into a stay-in-place gel.