Description
A spermicidal creams, foams, and jellies are chemicals that kill sperm.
Effectiveness
They are 95% effective but only work if combined with a barrier method such as a diaphragm or cervical cap.
Directions
You need to talk to your doctor before you use a spermicidal product of any type, once you know what you best option is, it should be applied to the inside of a woman's cervical cap or diaphragm. Then you simple insert the barrier as normal. Remember, you are attempting to cover the cervix, so sperm have to travel through the spermicide to get to the uterus.
Drawbacks
Vaginal spermicides are messy and annoying, have to be applied within a half hour of sex, will leave you with a chemical taste and smell down their and some have allergic reactions as well. If you have any issues such as rash or discomfort because of a spermicide you should stop using it.