From my research, there is a definite correlation between the dosage and severity of adverse reactions.

First of all, the most important factor is dosage PER DAY. Someone who takes 750mg/day of Levaquin for 1 week, is far more likely to suffer a more severe adverse reaction than someone who takes 250mg/day of Levaquin for 3 weeks. As the dosage per day increases, the danger of suffering a serious reaction exponentially rises.