esmirtazapine esmirtazapine esmirtazapine (org-50,081) is a tetracyclic antidepressant drug which was under development by organon for the treatment of insomnia and vasomotor symptoms (e.g., hot flashes) associated with menopause. esmirtazapine is the (s)-(+)-enantiomer of mirtazapine and possesses similar overall pharmacology, including inverse agonist actions at h1 and 5-ht2 receptors and antagonist actions at α2-adrenergic receptors. esmirtazapineclinical dataroutes ofadministrationoralatc codenonelegal statuslegal status in general: uncontrolled pharmacokinetic datametabolismliver (cyp2d6)elimination half-life10 hoursidentifiers iupac name (s)-1,2,3,4,10,14b-hexahydro-2-methylpyrazino(2,1-a)pyrido(2,3-c)(2)benzazepine cas number61337-87-9 ypubchem cid3085218e. maleate: 6451144drugbankdb06678 nchemspider2342166 yunii4685r51v7mkeggd04055 yecha infocard100.056.994 chemical and physical dataformulac17h19n3molar mass265.360 g·mol−13d model (jsmol)interactive imagemelting point114 to 116 °c (237 to 241 °f)solubility in watersoluble in methanol and chloroform mg/ml (20 °c) smiles cn1ccn2c3c(cccn3)cc4ccccc42c1 inchi inchi=1s/c17h19n3/c1-19-9-10-20-16(12-19)15-7-3-2-5-13(15)11-14-6-4-8-18-17(14)20/h2-8,16h,9-12h2,1h3/t16-/m1/s1 ykey:ronzaemnmfqxra-mrxnpfedsa-n y ny (what is this?) (verify) notably, esmirtazapine has a shorter half life of around 10 hours, compared to r-mirtazapine and racemic mixture, which has a half-life of 18-40 hours. merck has run several studies on low dose (3 - 4.5 mg) esmirtazapine for the treatment of insomnia. it is attractive for treating insomnia since it is a potent h1-inhibitor and a 5-ht2a antagonist. unlike low-dose mirtazapine, the half life (10 hours) is short enough that next-day sedation may be manageable, however, for people with cyp2d6 polymorphisms, which constitute a sizable fraction of the population, the half-life is expected to be quite a bit longer. merck researchers claimed that the incidence of next-day sedation was not a problem in one of their studies, but this claim has been challenged (15% of patients complained of daytime sleepiness vs 3.5% in the placebo group). in march 2010, merck terminated its internal clinical development program for esmirtazapine for hot flashes and insomnia, "for strategic reasons".