This is my second Rx for this stuff, only 250 mg., but I'd hate to see what would happen with a stronger dose! I was given this Rx to prevent infection after oral surgery. Within hours of taking it, that familiar itchy, burning sinus sensation started. I took an antibiotic to give me a sinus infection?? I already have tinnitis, and it is worse than usual. I feel awful with this stuff. I will tell my doctor that I will NOT take it again.