ine ▁atom ▁at ▁the ▁C 6 - position ▁of ▁the ▁related ▁qu in ol one ▁basic ▁mole cular ▁structure . ▁ ▁Even ▁though ▁this ▁was ▁the ▁first ▁flu oro quin ol one , ▁it ▁is ▁often ▁over look ed ▁when ▁class ifying ▁the ▁dru gs ▁within ▁this ▁class ▁by ▁gener ations ▁and ▁ex cluded ▁from ▁such ▁a ▁list . ▁ ▁Though ▁used ▁frequently ▁to ▁treat ▁farm ▁animals ▁and ▁on ▁occasion ▁household ▁p ets , ▁fl um equ ine ▁was ▁also ▁used ▁to ▁treat ▁ur inary ▁tract ▁in fe ctions ▁in ▁humans . ▁ ▁Fl um equ ine , ▁was ▁used ▁trans ient ly ▁treat ▁ur inary ▁in fe ctions ▁until ▁oc ular ▁to x icity ▁was ▁reported . ▁as ▁well ▁as ▁li ver ▁damage ▁and ▁an ap hy la ctic ▁shock . ▁ ▁In ▁ 2 0 0 8 , ▁the ▁United ▁States ▁Food ▁and ▁D rug ▁Administration ▁( F DA ) ▁requested ▁that ▁all ▁qu in ol one / flu oro quin ol one ▁dru gs ▁package ▁inser ts ▁include ▁a ▁Black ▁Box ed ▁Warning ▁concerning ▁the ▁risk ▁of ▁sp ont aneous ▁tend on ▁ru pt ures , ▁which ▁would ▁have ▁included ▁fl um equ ine . ▁ ▁The ▁F DA ▁also ▁requested ▁that ▁the ▁manufact ur ers ▁send ▁out ▁D ear ▁Doctor ▁Let ters ▁regarding ▁this ▁new ▁warning . ▁ ▁Such ▁tend on ▁problems ▁have ▁also ▁been ▁associated ▁with ▁fl um equ ine . ▁ ▁D rug ▁resid ue ▁The ▁use ▁of ▁fl um equ ine ▁in ▁food ▁animals ▁had ▁spark