I took 500mg of Levaquin once a day for two days. I stopped taking it because of the frightening side effects that I experienced. The doctor prescribed the antibiotic for a mild case of campylobacter. I normally never take medicine for anything, but the doctor assured me that this antibiotic was very strong and would take care of my problem. However, after a few hours after the first dose I began to experience a rapid heart beat, tightness of the chest, and about once every fifteen minutes I could feel my heart skip a beat. Unfortunately, I took another dose the following day, but I experienced much of the same. I stopped taking it after that because I thought that no treatment was worth these effects. It has been 3 days since I took my last dose and my heart is still racing and skipping beats. I told my doctor and he told me that this was just a common side effect of levaquin when caffiene is mixed with levaquin. But I have avoided caffiene for days. It's very scary to have something wrong with your heart when you are otherwise very healthy. I hope these symptoms leave because it's driving me crazy!!!!