We will now discuss spermicides, which are chemical barriers.
For thousands of years, women have put materials ranging from
rags to herbal preparations into the vagina in an effort to
prevent pregnancy. Modern science built on this approach and
developed products that are proven to kill sperm.
Spermicides consist of two components, a spermicidal chemical
and a delivery base for the chemical. The base can be a cream,
jelly, foam, film, suppository or tablet. The spermicidal chemicals
most often used today are nonoxynol-9 (N-9), menfegol and benzalkonium
chloride (BZK). Comparative data on the relative effectiveness
of different delivery systems or chemical formulations are scarce.
Most research has been done using N-9 since it is the most common
spermicide in the world.
The spermicidal agent kills sperm and STD microorganisms. Most
spermicides are surfactants, which means they act on the membrane
of the sperm or microorganism. In addition, some of the delivery
bases physically block the cervix to prevent sperm and microorganisms
from moving into the womans uterus, providing a secondary
mode of action.
Spermicides can be used alone or with another contraceptive
method. They are available without prescription in most countries,
but may be expensive.