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Does Bactrim effect your birth control pill?

By Anonymous September 9, 2015 - 8:31am
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Hello Anonymous,

Welcome to EmpowHER. That is a very good question.

Antibiotics taken by mouth can potentially decrease the effectiveness of birth control pills, specifically estrogen-containing oral contraceptives.

This occurs because, in addition to killing the bacteria responsible for causing the current illness or infection, oral antibiotics also kill the normal bacteria that live in the stomach, which are responsible for activating the birth control pill.

As a result, the oral contraceptive may be less effective. Spotting - or 'mid-cycle' bleeding - may be the first sign that an antibiotic is interfering with your birth control pills and lowering their effectiveness.

Antibiotics that have been shown to interact with birth control pills include rifampin (Rifadin®), and to a lesser extent, penicillin, amoxicillin, ampicillin, sulfamethoxazole/trimethoprim (Bactrim®), tetracycline, minocycline, metronidazole (Flagyl®) and nitrofurantoin (Macrobid® or Macrodantin®).

To avoid pregnancy while taking an antibiotic, and for at least one week afterward, doctors generally recommend using a condom or spermicide as a back-up method of birth control in addition to remaining on birth control pills.

Check with your doctor about how long you should continue to use a back-up method.


September 9, 2015 - 8:56am
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