Years ago when I had chronic Lyme disease, I was getting weekly intramuscular bicillin injections (I did this for 18 months). My LLMD also prescribed probenecid (if I remember correctly) which I took everyday. The probenecid was supposed to help the bicillin stay in my system longer. So, I am thinking that maybe with your increased fluid intake that you may actually be eliminating the medication from your system more quickly! I would ask your doctor what he thinks! But in my case, I always feel more comfortable talking to others who are going thru similar health problems!!!