My doc prescribed levofloxacin, 500mg once a day for 21 days, due to a low level chronic sinus infection that had flared up. I got near immediate relief from the worst effects of the infection but have experienced a rather extreme metallic taste in my mouth. I've used a tongue scrapper and that helps for short periods. The other item that seems to help is chewing Altoids cinnamon gum. I ran across another web site that recommends rinsing with a solution of 8 oz water with 1/4 teaspoon of baking soda. Other than the metallic taste, I haven't had any adverse reactions. Good luck to all.