The name tetracyclic is derived from the drug's molecular structure which consists of four ring like structures (compare tricyclic antidepressant).
Maprotiline, trade named Ludiomil®, and Mirtazapine, trade named Remeron® in the USA, Zispin® in Europe and Avanza® in Australia, are the only two drugs from this group widely used for the treatment of clinical depression. The tetracyclic antidepressant Mianserin was previously available internationally, however in most markets it has been phased out in favor of Mirtazapine.
Research on other tetracyclic antidepressant compounds (for example setiptiline) have been reported in the scientific literature. These other tetracyclic antidepressants are not publicly available.