Clarithromycin
"Worst medication ever. Was prescribed for strep throat...the swollen tonsils and pain in my throat has subsided, however, the first dose made me so weak I almost passed out....now it's day 3 and I have severe abdominal cramps, diarrhea every 10 to 20 minutes for the past 6 hours, gas all day long; and I feel faint here and there. I called my doctor and he switched me to a zpak starting tomorrow morning. I can't wait til this is over."