Antibiotic Interactions

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Question

Do antibiotics reduce the effectiveness of birth control pills?

Answer

Antibiotics taken by mouth can potentially decrease the effectiveness of birth control pills (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 (known as norma flora) that 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®).

Topical antibiotics such as Walgreens Triple Antibiotic Ointment or Neosporin® are not significantly absorbed into the bloodstream and therefore do not kill the normal flora in the stomach. As a result, topical antibiotics are not expected to reduce the effectiveness of oral contraceptives.

Back-up Birth control while taking antibiotics

Cases of contraceptive failure associated with oral antibiotics have been reported, but are not well-documented. To help women avoid pregnancy while taking an antibiotic - and for at least one week afterward - doctors generally recommend they use a condom or spermicide as a back-up method of birth control in addition to remaining on birth control pills. If you are taking both antibiotics and birth control pills, be sure to check with your doctor about how long you should continue to use a back-up method.

Get more information about your brand of birth control pills.

Learn more about birth control options in the Health Encyclopedia.

View Walgreens.com intimacy and sexual wellness products for over-the-counter contraception options.

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