Yes, I agree with BorederGirl, most antibiotics do effect your BC. Most of them include: rifampin (brand name Rifadin), penicillin, amoxicillin, ampicillin (Omnipen), cotrimoxazole (Septra or Bactrim), tetracycline (Sumycin), minocycline (Minocin), metronidazole (Flagyl), and nitrofurantoin and (Macrobid or Macrodantin). Just make sure you look at what your taking first and see if any of these are in your antibiotics ok! Hope it helps!:)