Antibiotics and Birth Control Pills

Although certain medications, such as rifampin and griseofulvin, are known to decrease the effectiveness of birth control pills, clinical studies have not shown a clear interaction between most antibiotics and birth control pills. Even so, if you are in a situation where it is important that you do not become pregnant, make sure to use a non-hormonal backup method of contraception (such as condoms) while taking an antibiotic.

Do Birth Control Pills and Antibiotics Interact?

Birth control pills, also known as "the pill" or oral contraceptives (OCs), are widely used throughout the world. While birth control pills can be prescribed for a number of reasons, they are most often used to prevent pregnancies in women of reproductive age. It is estimated that up to 100 million women use oral contraceptives, making them one of the most popular forms of contraception.
Antibiotics are also medications that are commonly prescribed, often for only short periods of time, to treat various types of infections. It is estimated that around 11 million kilograms of antibiotics are prescribed every year in the United States.
Reports of women who experienced accidental pregnancies while taking birth control have fueled an ongoing debate over whether or not antibiotics cause birth control pill failure. However, clinical studies have not yet found that an interaction exists between birth control pills and most antibiotics.

How Can Antibiotics Interact With Birth Control Pills?

While clinical studies have not shown that there is a clear interaction between birth control pills and most antibiotics, there have been case reports of individuals who have shown large decreases in the amount of ethinyl estradiol (a main hormone in birth control pills) when birth control is taken at the same time as antibiotics.
With these lower amounts of ethinyl estradiol in the bloodstream, there is an increased risk of having a birth control failure and becoming pregnant. However, it is still uncertain how significant this interaction may be with most antibiotics.
The exact way that the two medications interact is not known at this time. The decreases in the amount of birth control in the body could be possibly due to an increase in the breakdown (metabolism) or a decrease in the absorption of the ethinyl estradiol in the body after being taken at the same time as antibiotics.
It is important to know that while a clear interaction has not been found with most antibiotics, there are two anti-infective medications that are known to decrease the effectiveness of birth control pills. These medications are rifampin (rifampicin, Rifadin®) and griseofulvin (Grifulvin V®, Gris-PEG®).
Rifampin is a medication used to treat various infections and tuberculosis (TB). If you must take rifampin while on birth control pills, it is recommended that you use a non-hormonal backup method of contraception, such as condoms, while you are on rifampin and for one month after you stop taking rifampin. Rifampin can stay in your body for a period of time, even after you stop taking it. During that month, the rifampin can interact with your birth control pills and put you at an increased risk of becoming pregnant.
Griseofulvin is used to treat fungal infections. You should use a non-hormonal backup method of contraception, such as condoms, while you are taking griseofulvin and for one week after stopping griseofulvin as well.

More Headlines in Antibiotics and Birth Control Pills

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Last reviewed by: Kristi Monson, PharmD
Pregnancy and Pain