Will my birth control microgestin 1/20 be less effective while taking cefuroxime 500 mg? how long do i have to use alternative contraception?

The idea that antibiotics making birth control less effective is based on a self-reporting database in Europe and old studies. The theory is that antibiotics reduce gut bacteria necessary to metabolize estrogen, but is unproven. The only antibiotic proven to decrease estrogen and progestin levels is Rifampin. Abstinence is advised if still concerned or have a history of unintended pregnancies