About Mirtazapine Tetracyclic Antidepressant, piperazino-azepine group, Antidepressant. Mechanism of Action of Mirtazapine Mirtazapine antagonizes alpha 2 adrenergic receptors, 5HT2 and 5HT3 receptors. This will enhance noradrenergic and serotonergic activities. Mirtazapine also has potent antihistamine activity. The increase in concentration of neurotransmitters produces antidepressant activity. Indications for Mirtazapine Depression Interactions for Mirtazapine Drugs that are metabolised by and/or inhibit cytochrome P450 enzymes: Mirtazapine is not a potent inhibitor of various cytochrome P450 enzymes. Alcohol: Impairment of cognitive and motorskills produced by mirtazapine has been shown to be additive to those produced by alcohol. Patients are advised to avoid alcohol while taking mirtazapine.