Mirtazapine N-Oxide

Mirtazapine N-Oxide is an oxidation derivative of mirtazapine, featuring a tetrahydroisoquinoline N-oxide core substituted with a 3-methoxyphenyl group and an N′-cyclopropylideneamido moiety. The N-oxidation at the tetrahydroisoquinoline heterocycle introduces an electrophilic oxygen atom, altering electronic properties and reactivity relative to the parent compound. This impurity arises via oxidative degradation pathways during synthesis or storage, forming a stable, polar byproduct. It serves as an HPLC reference standard for quantifying oxidation-related impurities in mirtazapine formulations.