4-[4-(4-Chlorophenyl-d4)-3,6-dihydro-1(2H)-pyridinyl]-1-(4-fluorophenyl)-1-butanone is the labeled analogue of 4-[4-(4-Chlorophenyl)-3,6-dihydro-1(2H)-pyridinyl]-1-(4-fluorophenyl)-1-butanone (C376580), a dehydrated metabolite of haloperidol that can be biotransfomed by humans to Haloperidol pyridinium (HPP+), a potential neurotoxic found in the brain.