Harmane-d2 is the deuterium labeled Harmane. Harmane, a β-Carboline alkaloid (BCA), is a potent neurotoxin that causes severe action tremors and psychiatric manifestations. Harmane shows 1000-fold selectivity for I1-Imidazoline receptor (IC50=30 nM) over α2-adrenoceptor (IC50=18 μM) . Harmane is also a potent and selective inhibitor of monoamine oxidase (MAO) (IC50s=0.5 and 5 μM for human MAO A/B, respectively) [1][2][3][4].