There are some exceptions
But Dr. Kimberly Jean, a board-certified physician who focuses on reproductive health, notes that there's one particular antibiotic that will interfere with the pill's effectiveness.
This antibiotic is known as rifampin (or Rifadin), a member of a class of drugs called antimycobacterials. Predictably, these drugs fight mycobacteria, most notable for causing tuberculosis and leprosy. According to Dr. Jean, this class of antibiotics causes estrogen to be metabolized and broken down fairly quickly in the liver. As a result, estrogen levels plummet. When this happens, as Dr. Monya De, MD MPH, puts it, "No estrogen, no stopping of ovulation."
Since birth control prevents your body from ovulating, and therefore from giving a determined sperm the chance to connect with an egg, the normally slim chance of becoming pregnant turns into a real possibility.