The Link Between Antibiotics and Birth Control

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


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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