I am wondering what is the medicine By-Mycin used for? My brother is taking it for a sore eye, but I cannot see it under the Mycin category. ## I was prescribed By-Mycin over a year ago and am wondering what I took them for. I did have a sinusitus infection and maybe that's what they were prescribed for? I'm clearing out my medicine cabinet and came across the empty packet. ## I have been prescribed By-Mycin for a sty on the outside of my eye. I had fluclon before this. Which is the best to use?