Hi Aaron: There is no research that shows that Lexapro has any effect on contraceptive pills, but you should speak with a gynecologist about this first. While all of the SSRI's have decreased libido as a potential side effect, they are not known to "cancel out" the pill. Read more about Lexapro here.   Regards, Dr. Diana Walcutt   *Dr. Walcutt is a Psychologist. Dr. Walcutt's answers are not intended to diagnose or treat any medical or mental disorder. Any information given in a post about medication is for educational purposes only, and primarily to aid you in having an informed discussion with your own Psychiatrist/Physician.