bacterial infection
"Nightmare.  2 hours after taking it chest hurt,  experienced urination retention (I had to concentrate to release pee) yikes. Could not lie back without heart feeling like it will explode.  I think the medicine was trying to kill me. Throat felt weird beyond words. My uncle is a dentist and said this is one antibiotic to QUIT and NOT finish the bottle.  I read about people who stuck it out and continued through the bizarre symptoms and side effects and they regretted it.  Sick for months after quitting"