Ask a doctor on the topic of Internal medicine

Very late onset and side effects of antibiotics

August 22, 2017 | 25,00 EUR | answered by Dr. med. Frauke Gehring

Good day,

I had to take antibiotics (Penicillin) for a bacterial infection. However, the effects only started to show several days AFTER the LAST dose. Although I already felt an improvement in symptoms 2-3 days after the first dose, they only completely disappeared several days after the last dose.

I have also been feeling quite weak since around the same time, while during the time of taking the antibiotics and shortly after, I was surprisingly feeling well (besides some loose stool, I had no side effects).

Therefore, my question to you is: Is it possible for antibiotics to only start working properly and effectively days AFTER the end of the therapy? And can delayed side effects also occur? If so, what can be done to alleviate the side effects that occur later? (I am almost certain that my current weakness has something to do with it - there is nothing else present that could be a reason for it).

Kind regards,

Dr. med. Frauke Gehring

Hello,

First of all, it may not necessarily have been (solely) a bacterial infection. Antibiotics do not help against viruses, and if there were any, or if they were also present, it takes the natural course of 2 to 3 weeks for an infection to clear up.

Antibiotics always start to take effect after at most 2 days. The only delayed side effect is an allergy with itchy skin rashes. Your fatigue is probably due to the ongoing infection. Or you may have picked up a new virus due to the slightly inhibited immune response from the antibiotic, which you are now fighting.

In any case, you still need to rest.

Take care!

Warm regards, Dr. Gehring