[Pharmacological study of Mequitazine (LM-209). (V). Pharmacological actions of a main metabolite of LM-209, mequitazine sulfoxide (LM-209 SO) (author's transl)].

The pharmacological action of a main metabolite of Mequitazine (LM-209), Mequitazine sulfoxide (LM-209 SO), was compared with data on LM-209 to investigate whether LM-209 is metabolized in vivo to the active form and if it has pharmacological actions. In the excised ileum of guinea-pigs, the anti-histaminic and anti-cholinergic activities of LM-209 SO were about 1/8 and 1/20, respectively, of LM-209. The protective activity of LM-209 SO on sudden death induced by histamine in mice was about 1/2.5 of LM-209. Acute toxicity of LM-209 SO given orally to mice was 1/3 of LM-209. In the EEG of rabbits, LM-209 SO did not affect the spontaneous pattern or the arousal and recruiting responses. The mydriatic and local anesthetic activities of LM-209 SO were significantly less than those of LM-209. Thus, the pharmacological activities and toxicity of LM-209 SO were significantly less potent than those of LM-209.