Expert: Michael S. Fisher, <B>Ph.D., M.D.</B> - 10/8/2004

Question
I have what can be described as adult cystic acne.  I have just been prescribed 250 mg daily of cephalexin by my doctor.  He assures me that this low of a dose will not interfere with my birth control pills.  What is you opinion?

Answer
What you ask is brings up a controversy.  Some antibiotics can decrease the effect of birth control pills by 3% but this is enough to make the birth control less effective.  Where I trained the only oral medication given to women on birth control pills was Erythromycin.  I have been to meetings that state that there is also the possibility that women can get pregnanct on birth control pills without the presence of antibiotics.  Ask your doctor if he will pay for the child if you get pregnant? If you are really worried about getting pregnant then use two forms of birth control while taking the Cephalexin.