Nuvaring and Antibiotics - Still effective?

Dear Ask The Doctor: My fiance is using Nuvaring. She started three weeks ago. At the beginning of the first week, she inserted the ring. At the beginning of the second week, she began taking antibiotics for the flu. We're coming up on the end of three weeks where the ring is removed for the ring-free week where she should have her period. At the end of the ring-free week is our wedding, and sometime then we will have sex. We read online that antibiotics can affect the efficiency of hormonal birth control, and that extra precautions such as condoms should be used for the week after the antibiotics are no longer taken. Our question was if the antibiotics affected the ring during week 2 and week 3, is week 4 protected anyways? And if not, when the new ring is put in at the beginning of a new 4-week cycle, should we take extra precautions until the new ring has been in for 7 days?

Dear Erin: It is true that the efficacy ( ie the effectiveness ) of the OCP's does reduce when taken concomittantly with antibiotics . However the nuva ring is applied locally and thus the hormones are released locally and there is little or no metabolism it goes through as it does not enter the systemic circulation and thus there is little effect on the efficacy when taken with antibiotics. However, since no contraceptive measure is 100%, it is still adviced to use back up protection during that time period. I hope this helps.