Mianserin's mechanism of therapeutic action is not well understood, although it apparently blocks alpha-adrenergic, histamine H1, and some types of serotonin receptors.
Mianserin is a tetracyclic antidepressant that has antihistaminic and hypnosedative, but almost no anticholinergic, effect. It is a weak inhibitor of norepinephrine reuptake and strongly stimulates the release of norepinephrine. Interactions with serotonin receptors in the central nervous system have also been found. Its effect is usually noticeable after one to three weeks. Mianserin may cause drowsiness and hematological problems.
Oral rat LD50: 780mg/kg