Eli5 – why do you take antibiotics as a course and not all at once?

Question

I’ve just started an antibiotics course which is 4 times a day for 10 days and that got me wondering if they would be just as effective if I took them all and why not.

In: 674

Answer 1

A number of folks have mentioned that antibiotics (abx) are excreted from your body rather quickly. What’s happening is that most of the abx excreted (let’s call it 75% but it varies wildly) but only a portion is absorbed (20%) and only a small portion (5%) makes it to where the infection is. You need multiple doses to have enough abx where it does some good; you can’t do it all at once (anymore than you can drink 5 gallons of water all at once).