More than or more then? They mean different things.
I had a 3-year streak of running everyday going in high school once and got strep throat. It hampered my ability quite a bit. They PRE-scribe you ampicillin or something like that. It is very fast acting. I think I was on it for 4-5 days. I trained through it while taking the drugs and we had 1-2 meets a week so I could not sit out those.
I was in about 10:20 shape and ran one race while sick and on the drugs and split 5:20/5:45 for 11:05. One week later we had the last race of the year and I ran 5:12/5:23 for 10:35 while still sick.
I felt like in one week more I could have been back at top shape.
The anti-biotics are not a worry. They may make you feel bad, but they won't kill you.