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What is an antibiotic?

Antibiotics are used for the treatment of bacterial infections like urinary tract infections, ear infections, gastrointestinal infections, and respiratory infections.

Antibiotics are classified based on their spectrum of activity, chemical structure and the mechanism by which they work against bacteria.

Antibiotics are classified into bacteriostatic and bactericide.

Bacteriostatic antibiotics interfere with the protein synthesis of the bacteria, while antibiotics that interfere with bacterial enzymes, cell wall and membrane of the cell are called bactericidal antibiotics.

Based on the spectrum of bacteria they work on, antibiotics are classified into antibiotics with a narrow spectrum (usually work against one or couple types of bacteria, like again gram positive or gram negative bacteria) and antibiotics with a broad spectrum (usually work against a wide range of bacteria).

Antibiotics are usually administrated orally, but in more serious infections they can be administrated intravenously.

Antibiotics are very safe when used correctly. They have few side effects, but as with most medications, antibiotics can interfere with other drugs. One of them are birth control pills.

Always keep in mind that antibiotics don't cure viral infections.

Take antibiotics as prescribed by your doctor. If you feel better never stop the treatment, but finish it all. Not finishing your course of treatment means your infection can return, and this time maybe even worse than the first time. Not taking the antibiotics correctly will result in antibiotic resistance.

How do antibiotics interfere with birth control pills?

There are two ways how antibiotics can interfere with birth control pills:

  • Reducing the re-circulation of estrogen in the body
  • Increasing the breakdown of estrogen into metabolites in the liver

Normally birth control pills are metabolized in the liver, and these metabolites are then secreted into the intestines of the gastrointestinal tract, with the help of bile secreted from the liver. Normal bacterial flora which is always present in the intestines is able to convert these metabolites into active estrogen, which is reabsorbed into the body. Antibiotics can kill the normal bacterial flora of the intestines, which will make the birth control pills less effective. This is only theoretically explained, and it has never been proven that pregnancies actually occur due to the reduction of the re-circulation of estrogen.

The increased breakdown of estrogen into metabolites in the liver will reduce the amount of active estrogen in the body, even though they might be more non active estrogen-metabolites. The decreased levels of estrogen in the body can result in unwanted pregnancies.

Since it is better to be safe than sorry, use another birth control method while taking antibiotics if you don't want to get pregnant. Condoms are a safe and easy temporary birth control method.

The failure rate of birth control pills due to use of antibiotics at the same time is very low, measured somewhere at about one percent.

One of the antibiotics that is known to interfere with birth control pills is Rifampin.

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