The effectiveness of any type of estrogen-containing birth control pill may be impaired during treatment with some types of antibiotics. However, the risk is very slight, and the supportive evidence is primarily limited to anecdotes from case reports and findings from uncontrolled or poorly controlled studies. In fact, according to Contraceptive Technology, 19th Edition, it is not necessary to use a back up method of birth control while on antibiotics because they do not lower the levels of hormones in your blood to the point that you would be at risk for pregnancy. The only exception is the medication, rifampin (which is primarily used to treat tuberculosis). To be on the safe side, however, we do recommend that our pill-users also use condoms or abstain from sex during antibiotic treatment and for at least one week after.
As long as you have been taking your birth control pill at the same time every day, pregnancy is highly unlikely. If you are a week or more late for your period, take a pregnancy test. If it is negative, repeat the test every two weeks until you have a normal period or a positive test result. Do not stop taking the pill unless you test positive for pregnancy. You should also be aware that some medications can cause menstrual irregularities so don’t panic if your next period comes later than normal or is lighter or heavier than usual.
For future reference, the following drugs or herbal products can decrease the effectiveness of the pill:
- barbiturates
- bosentan
- carbamazepine
- felbamate
- griseofulvin
- oxcarbazepine
- phenytoin
- rifampin
- St. John’swort
- topiramate
- HIV protease inhibitors or non-nucleoside reverse transcriptase inhibitors
15. August 2012
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