urinary tract infection
"I used Cipro for a urinary tract infection (I do not usually get urinary tract infections).  The first night I took it, I felt better by the next morning.  It took a few hours before I felt better (where I didn't have to go to the bathroom every 3 minutes), but it let me sleep and by the next day that burning sensation had gone away.

The only side effect, was I felt nauseated and sluggish the first day.  After that, it was great to get back to normal."