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after anitbiotics when is the pill safe again?

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I have been on birth control pills for over a year now (tri-legest Fe 28 day). I started antibiotics on Feb. 7th for a bacterial infection and was on the antibiotics for seven days and ended on the 14th. During the time i took the antibiotics, i was on the third week of pills. I continued taking the pills and I got my period on tuesday the 22nd. It was a normal period and lasted its normal length around three days. While i was on antibiotics, i used a back up method and am still using a back up method because i am unsure of exactly how long the antibiotics are in my system and when birth control is 99% effective again. I started a new pack of pills on sunday the the 20th and have taken every pill on time. So my question is when can i start having unprotected sex or sex without a backup method again since i am on the pill?

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replied March 7th, 2011
Birth Control Answer A20457
Welcome to ehealthforum.
Few antibiotics can still be in your system even after 15 days. It would be wise to continue using back-up birth control measures until 30 days are up since you took your last antibiotic pill. After that you can resume having intercourse as usual.
Take care.

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