Some cannot be used by individuals with certain medical problems. They should be inserted into the vagina within an hour before intercourse. If intercourse is repeated. The active ingredient in most spermicides is the chemical nonoxynol-9. The failure rate for spermicides in preventing pregnancy when used alone is from 20 to 30 percent.
Spermicides are available without a prescription.
People who experience burning or irritation with these products should not use them. In each instance, the method works by keeping the sperm and egg apart. Usually, these methods have only minor side effects. The main possible side effect is an allergic reaction either to the material of the barrier or the spermicides that should be used with them. Using the methods correctly for each and every sexual intercourse gives the best protection.