Glemanserin (INN; MDL-11,939) is a drug which acts as a potent and selective 5-HT2A receptor antagonist. The first truly selective 5-HT2A ligand to be discovered, glemanserin resulted in the development of the widely used and even more potent and selective 5-HT2A receptor antagonist volinanserin (MDL-100,907), which is a fluorinated analogue. Thou...