Women taking birth control pills should be mindful of the possible interaction between oral contraceptives and the medications recommended by the Federal Centers for Disease Control and Prevention (CDC) to treat anthrax. The CDC recently recommended that antibiotic and anti-infective medications, such as Cipro, doxycycline, and penicillin, be used to treat those believed to have been exposed to anthrax spores. Many antibiotics are known to interfere with the efficacy of oral contraceptives in preventing pregnancy.
In clinical studies, antibiotics have been shown to diminish the effectiveness of birth control pills. Studies have shown that birth control pills, which are typically 98% effective in preventing pregnancy, are significantly less effective when they are taken at the same time as some antibiotics. This interaction is commonly known within the medical community and is noted in the prescribing information for leading antibiotics and for oral contraceptives.
There have not been any clinical studies on the effects of Cipro, an anti- infective medication, on the failure rate of oral contraceptives. However, because Cipro is similar to antibiotics in several ways, including the types of bacteria that it targets, some healthcare providers suggest that it could inhibit the efficacy of birth control pills.