What is "phenylethylidenehydrazine"

n. A GABA transaminase inhibitor with similar efficacy to vigabatrin.

Phenylethylidenehydrazine (PEH), also known as 2-phenylethylhydrazone or β-phenylethylidenehydrazine, is an inhibitor of the enzyme GABA transaminase (GABA-T). It is a metabolite of the antidepressant phenelzine and is responsible for its elevation of GABA concentrations. PEH may contribute to phenelzine's anxiolytic effects.