Mirtazapine has a tetracyclic chemical structure unrelated to selective serotonin reuptake inhibitors (MAOI). Mirtazapine belongs to the piperazanoazepine group of compounds and is an analogue of Mianserin. It is designated 1,2,3,4,10,14b-hexahydro-2-methylpyrazino [2,1-a] pyrido [2,3-c] benzazepine and has the empirical formula of C17H19Cl3. Its molecular weight is 265.36.
Mirtazapine is a white to creamy white crystalline powder which is slightly soluble in water.