I am on birth control pills, and I am having to take an antibiotic (1 dose 2x daily for the next 10 days) for a sinus infection. How might the antibiotic affect the effectiveness of the pill, and how long after I'm done with the antibiotic can I start trusting the pill again? Also, should I expect any irregularities with my period? Thanks for your time.
There is theoretically a risk of antibiotics interfering with optimal absorption of your synthetic hormones, which can lead to ovulation and potentially fertilization/implantation of a pregnancy. The standard recommendation is to use a back up contraception through the entirety of the current cycle until your next menses. It is not unusual to experience spotting while on antibiotics if you are on synthetic hormones.