flucloxacillin is a broad spectrum antibiotic it is usually used skin infections such as acne, in growing toe nails that have become infected etc it isn't used for things like cheast infections etc.eport Abuse. Flucloxacillin (a.k.a. floxacillin) is a fluorinated cloxacilin. It is a narrow spectrum penicillin family antibiotic that is used to treat penicillin resistant bacteria. (betalactamase producers). It is related to dicloxacillin.