Mirtazapine is a tetracycline antidepressant. It is a norepinephrine (NA) and specific 5-HT antidepressant. Mirtazapine can block the cell body and nerve endings of Na ergic neurons α- Adrenoceptors. The former enhanced the discharge activity of Na ergic neurons, while the latter enhanced the release of Na ergic neurons. As Na ergic neurons also projected to the nucleus raphe where 5-HT ergic neurons were located, mirtazapine blocked Na ergic neurons α 2-adrenoceptor increases the release of Na. Na acts on 5-HT neurons α 1-adrenoceptor, which enhanced the discharge of 5-HT neurons and increased the release of 5-HT in nerve endings. Therefore, mirtazapine is considered to be an antidepressant with dual mechanism of action. In addition, mirtazapine blocks 5-HT2 and 5-HT3 receptors and avoids the adverse reactions (such as insomnia and sexual dysfunction) caused by common drugs. Mirtazapine can be used to treat all kinds of depression. Symptoms such as lack of pleasure, psychomotor depression, poor sleep (wake up early) and weight loss are effective. It can also be used for other symptoms such as loss of interest in things, suicidal ideation and mood swings (good morning, bad evening). The drug takes effect after 1-2 weeks.