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.
The fact that you are a bit late for your period may simply be caused by your antibiotic use. Different types of medication can cause menstrual irregularities. Keep taking your pill at the same time every day. If you fail to have any bleeding at all during your sugar pill week, take a pregnancy test just to be on the safe side. Do not stop taking the pill unless you test positive for pregnancy.
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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