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How long does an antibiotic stay in your system after you've finished the prescription?
An_194933 posted:
I am on an antibiotic for 10 days. I will finish my prescription on the last day of my period (Saturday) and then will start my first pill of my birth control on that Sunday. Am I still protected during that time from pregnancy? Or do antibiotics stay in you system longer and could therefore cancel out my birth control that I start that Sunday. Also, if it the antibiotic stays in my system a couple days after I've finished the prescription, does that cancel out the whole month of birth control pills? Or just a few days?
tmlmtlrl responded:
Antibiotics do not cancel out your birth control! Supposedly there are a couple of stronger antibiotics that could lessen the effect of the BC but they do not cancel it out. The warning statements about BC on the antibiotics are more of a cya for the doctors and drug co. Also, not sure if this is your 1st pack of pills or if you've been on them awhile -- if it is your 1st pack of pills you are not protected from pregnancy for the first 3months (which is also a cya, but good advice)!!
tmlmtlrl responded:
FYI, this is something that you can call your doctor's office and ask a nurse about or even your pharmacist. They will answer your questions for free -- it's part of their job :)
kpc1234 replied to tmlmtlrl's response:
I am aware that I can contact my doctor but with my work schedule and the way the doctors are around here, we'd be playing cat and mouse for me to get a simple answer!!! I have been on bc for about 5 years now and have been told in the past (when I was on an antibiotic) that I would have to use alternative birth control during the whole month that I used an antibiotic because it lessens the effects of the bc (which is what I meant by canceling it out). I tried looking online but nowhere could I find the answer to how long antibiotics stay in your system.
tmlmtlrl replied to kpc1234's response:
My source here is from my doctor. I had this conversation with her and she said they do not affect the birth control, that is just something they need to say so that they are not held responsible for anything that might happen...sometimes people just get preg even on bc. However, I read a post that Gail responded to that said certain ones may actually have an affect. As far as the doctor part, what I'm saying is call and ask to speak with a nurse. I know I can do that at my dr office, they direct the phone call to the nurse's station. Or try the pharmacy because they are trained to answer these questions. My personal guess as to how long they stay in your system would be around 24 hrs....that is part of why you are supposed to 'take as directed' to keep the antibiotic consistant in your system. Like if you take it twice a day, you are supposed to space it out properly that it stays balanced in your system and if you don't take all the medication you can mess it up and have to do it over. So depending on how u take them i'm sure the answer varies, but they don't stay in your system for any real length of time past when you're done taking them. I do suggest making those calls though to put your mind at ease...remember your not calling the 'doctor' cuz trust me they get paid for their time (and it's not on the phone)!! The nurse will either answer or call back. I'm sure there are some times better to call than others -- like in the morning vs. late afternoon.

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