Q: Do antibiotics interfere with the effectiveness of birth control pills? — Susan Peterson, Jacksonville, Florida
A: This association emerged in the early 1970s, when women taking oral contraceptives reported high rates of irregular bleeding and unwanted pregnancies while being treated with a specific antibiotic called rifampin. For the sake of caution, women are still warned against relying on the Pill while taking antibiotics. Yet there's very little evidence that any drug other than rifampin interferes with the efficacy of the Pill. If you're really worried, you can use a condom as a backup, but it's generally unnecessary.