First, I've found out, to my astonishment, that whether Limbaugh knows how the contraceptive pill works or not, many on the wide and varied Internets do not seem to have that knowledge. So it might be worth stating that the pill works mainly by preventing ovulation:
Birth control pills prevent pregnancy through several mechanisms, mainly by stopping ovulation. If no egg is released, there is nothing to be fertilized by sperm, and the woman cannot get pregnant. Most birth control pills contain synthetic forms of two female hormones: estrogen and progestin. These synthetic hormones stabilize a woman's natural hormone levels, and prevent estrogen from peaking mid-cycle. Without the estrogen bump, the pituitary gland does not release other hormones that normally cause the ovaries to release mature eggs.Bolds are mine.
Second, some medications can interfere with the pill and its efficacy. It's best to check with your prescribing doctor to find a list of those based on the most recent information, but these are some medications which might affect the pill:
Medicines that can interact with the pill include:And a bit unrelated, but here you can find the advertisers which have stopped advertising with Rush Limbaugh.
some types of antibiotics..
some herbal remedies, such as St John's Wort
some anti-epileptic drugs (AEDs) used to treat epilepsy, such as carbamazepine
some antiretrovirals (ARVs) used to treat HIV, such as ritonavir