er ▁extent . ▁ ▁But ab ar b ital ▁is ▁met abol ized ▁almost ▁entirely ▁by ▁the ▁li ver , ▁products ▁including ▁polar ▁alco h ols , ▁k et ones , ▁phen ols , ▁or ▁car box y lic ▁ac ids , ▁before ▁it ▁is ▁ren ally ▁ex cret ed ▁in ▁the ▁ur ine . ▁ ▁Half - Life : ▁~ 1 0 0 ▁hr ▁D uration : ▁ 6 - 8 ▁hr ▁On set : ▁ 4 5 - 6 0 ▁min ▁En zym es ▁induced : ▁C Y P 1 A 2 , ▁C Y P 2 C 9 / 1 0 , ▁C Y P 3 A 4 ▁Ex cret ion : ▁Ur ine ▁ ▁Mechan ism ▁of ▁Action ▁ ▁The ▁mechanism ▁of ▁action ▁by ▁which ▁bar bit ur ates ▁ex ert ▁their ▁effect ▁is ▁not ▁yet ▁completely ▁understood , ▁however ▁they ▁are ▁believed ▁to ▁be ▁involved ▁in ▁the ▁enh ancement ▁of ▁G AB A ▁in hib itory ▁ne uro trans mit ter ▁activity ▁in ▁the ▁C NS ▁via ▁G AB AA ▁re cept ors . ▁But ab ar b ital , ▁as ▁a ▁member ▁of ▁this ▁drug ▁class , ▁ac utely ▁pot enti ates ▁in hib itory ▁G AB A erg ic ▁tone ▁by ▁binding ▁with ▁a ▁specific ▁site ▁associated ▁with ▁a ▁Cl − ▁ion op ore ▁at ▁the ▁G AB AA ▁re ceptor . ▁ ▁But ab ar b ital ' s ▁binding ▁causes ▁the ▁channel ▁to ▁remain ▁open ▁longer ▁and ▁thus ▁prolong s ▁post - syn apt