How long does it take for anti-biotics to leave the body?

Most antibiotics have a duration of no more than 24 hours which is why you take them often and for the full recommended course. If you stop them before recommended your infection can come back and will most likely be worse than before, because they build up a tolerance to the antibiotic. This specific drug's half life is 12 hours, so you are pretty safe to go drinking, however make sure you aren't cutting yourself short on your antibiotic to go drink. It probably could do little harm if you did not drink for one weekend out of the year.