CIS-THIOTHIXENE

In 2002, the American Association of Poison Control Centers’ Toxic Exposure Surveillance System reported 5224 human exposures to phenothiazines, thioxanthenes, and other neuroleptic medications; 3691 were in adults and 808 in children. Unintentional and intentional exposures accounted for 43.7 and 47.8%, respectively. There were 417 (8.0%) adverse drug reactions reported. Thioxanthenes are chemical compounds in which the oxygen atom in xanthene is replaced with a sulfur atom. They are also related to phenothiazines. Several derivatives are used as typical antipsychotics in the treatment of schizophrenia and other psychoses. The thioxanthenes, as a class, are closely related chemically to the phenothiazines. The major structural difference is that the nitrogen at position 10 in the phenothiazines is replaced by a carbon atom with a double bond to the side chain, as shown in the chemical structure of flupenthixol, which has a double-bonded carbon in the number 10 position. Clopenthixol is a typical antipsychotic drug of the thioxanthenes class and a racemic mixture of cis and trans isomers. Zuclopenthixol, the pure cis isomer, has been much more widely used. Both drugs are equally effective as antipsychotics and have similar adverse effect profiles, but clopenthixol is half as active on a milligram-to-milligram basis and appears to produce more sedation in comparison.