▁André ▁Bar be au . ▁Unfortunately , ▁other ▁investig ators ▁were ▁unable ▁to ▁rep licate ▁these ▁early ▁results , ▁and ▁the ▁use ▁of ▁D OP A ▁remained ▁in ▁question ▁until ▁ 1 9 6 7 , ▁when ▁George ▁Cot zi as ▁at ▁the ▁Brook h aven ▁National ▁Labor ator ies ▁in ▁U pton , ▁New ▁York , ▁used ▁meg ados es ▁of ▁D OP A , ▁up ▁to ▁ 1 6   gram s ▁per ▁day . ▁Not ▁long ▁after ▁these ▁results ▁became ▁known , ▁Curt ▁Por ter ▁at ▁Mer ck ▁showed ▁that ▁L - DO PA ▁was ▁the ▁active ▁s tere ois omer , ▁thus ▁reducing ▁the ▁effective ▁do se ▁to ▁half . ▁ ▁With ▁L - DO PA ▁identified ▁as ▁the ▁active ▁form , ▁Alfred ▁P let scher ▁and ▁his ▁colle agues ▁at ▁Hoff man - La Ro che ▁synth es ized ▁b enser az ide , ▁an ▁in hib itor ▁of ▁D OP A ▁dec ar box yl ase , ▁which ▁further ▁reduced ▁the ▁required ▁do se . ▁A ▁drug ▁combining ▁L - DO PA ▁with ▁b enser az ide ▁was ▁market ed ▁under ▁the ▁brand ▁name ▁of ▁Mad op ar . ▁Independent ▁work ▁was ▁carried ▁out ▁by ▁Victor ▁L otti ▁at ▁Mer ck ▁in ▁West ▁Point , ▁Pennsylvania . ▁Mer ck ▁had ▁already ▁synth es ized ▁and ▁pat ented ▁car bid op a , ▁another ▁do pa ▁dec ar box yl ase ▁in hib itor ▁in ▁ 1 9 6 2 , ▁and ▁in ▁ 1 9 7 1