Benzeneethan-α,α,β,β-d4-ol is an intermediate used in the synthesis of Phenelzine-d4 Sulfate (P595902), which is a labeled hydrazine derivative that is a non-selective and irreversible monoamine oxidase inhibitor (MAOI) and also inhibits GABA-transaminase (GABA-T), markedly increasing brain GABA levels. It is an antidepressant and anxiolytic used in the treatment of major depressive disorder (MDD) as well as other neural disorders.