Phenylethylidenehydrazine (PEH), also known as 2-phenylethylhydrazone or β-phenylethylidenehydrazine, is a GABA transaminase inhibitor.

[1][2] It is a metabolite of the antidepressant phenelzine and is responsible for its elevation of GABA concentrations.

[1] PEH may contribute to phenelzine's anxiolytic effects.

[3]