Nordoxepin

What it isThe N-desmethyl metabolite of doxepin, more noradrenergic and less antihistaminic than the parent.

Why it mattersIt shifts the balance of a doxepin dose from sedation toward noradrenergic effect as it accumulates.

What it changesIt is why doxepin becomes less sedating over weeks, and why the low-dose hypnotic indication uses doses too small to generate much of it.