Earlier studies seemed to indicate that if antibiotics and
birth control pills are taken simultaneously, more women got
pregnant than one would normally expect. Medications like
ampicillin and tetracycline are suspected of interfering
with the effectiveness of birth control pills. However, from
all the studies that saw this connection, they have shown
that antibiotics do not increase the pregnancy rate at all,
and points out that older information was not reliable
enough to draw conclusions about pregnancy rates on any of
the antibiotics. From recent studies, some reported
antibiotics show no signs in affecting the metabolism of
birth control pills. An example of such antibiotics include
Cipro, which does not alter metabolism; and Diflucan, a
product that does not decrease estrogen but actually
increases it.
Still, if one takes both antibiotics and birth control
products, the contraceptive may not work, therefore
increasing the chances of becoming pregnant. Oral
contraceptives or birth control pills work by affecting the
production of certain hormones that can stop a woman’s
ovaries from releasing eggs; or make the lining of the
uterus thinner so that fertilized eggs cannot attach to the
uterus; and it can make it harder for the sperm to reach the
eggs. All these are done by two hormones: the estrogens and
progestins.
The reason behind antibiotics and birth control when taken
together is that some antibiotics make it hard for the body
to absorb the hormones contained in birth control pills.
Other antibiotics makes the body get rid of the hormones
even faster, and if either of this happens, the lower
hormonal levels in the body may allow a woman to get
pregnant even if she does not want to. Such antibiotics
cause the enzymes in the liver to increase the break down of
estrogens and thereby decrease the levels of estrogens in
the body and the effectiveness of the birth control pills.
Some of the antibiotics with this kind of effect include
rifampin, penicillin, tetracyclines, and trimethoprim, among
others. Another reason on how antibiotics interfere with the
effectiveness of birth control pills is by the reduction of
re-circulation of estrogens within the body. Estrogens in
birth control pills are broken down by conversion in the
liver to other chemicals which are secreted into the
intestines in the bile produced by the liver. Bacteria in
the intestine are able to convert these chemicals back into
the active estrogen which is then re-absorbed into the
body.. This re-circulation is called entero-hepatic cycling.
Theoretically, antibiotics can kill the bacteria that
convert the inactive chemicals to the active estrogen, and,
therefore, may interfere with the effectiveness of birth
control pills. Unwanted pregnancies could occur. Although it
has not been proven that unwanted pregnancies can occur by
this means, drug manufacturers caution that antibiotics
could decrease the effectiveness of birth control pills.
However, other antibiotics will not affect contraceptive
implants. An implant is a capsule inserted under the skin on
the inside of a woman’s upper arm. This reduces the chances
of becoming pregnant by releasing progestin into one’s
bloodstream. To make sure that pregnancy prevention is at
hand, always inform the doctor if one is taking birth
control pills. The doctor may then prescribe another
medication, or discuss possible drug interactions. If in
case one is under prescription medications, one can still
take birth control pills only if there is a barrier form of
birth control. This includes the use of a condom, a
diaphragm, or a cervical cap.
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