Best Answer: Zanaflex will stay in your body at a maximum of 24 hours. I would say that after 3 days of not taking Zanaflex, if your blood was drawn, no trace of Zanaflex would be found. If you look at the package insert [information that the FDA approves and has to be with every medication], on the first page, second column there is a graph. It shows that after 1 dose, at 24 hours, there should be little or no Zanaflex in the bloodstream. Zanaflex also has a pretty short half life (~2 hours) so the graph matches.