Thiothixene (USAN:USP)

DescriptionIn 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.

UsesThioxanthenes are used as neuroleptic agents, antipsychotics, and major tranquilizers in the treatment of psychosis, including schizophrenia, senile psychosis, pathological jealousy, and borderline personality disorder. Other uses include the treatment of pain, postoperative neuralgia, sedation, anxiety neurosis, childhood behavior problems, and depression. The maximum therapeutic daily oral dose for chlorprothixene, flupenthixol, and thiothixene is 600, 224, and 60 mg, respectively; the maximum intramuscular doses are 200 mg day-1, 100 mg weekly, and 30 mg day-1, respectively. Some thioxanthenes and thioxanthenones have shown signs of possible human therapeutic potential against tumors in mice and in vitro assays, and some thioxanthenes have been shown to have cytotoxic and antimicrobial activities. Chlorprothixene is primarily indicated in conditions such as agitation, mania, psychosis, schizophrenia, and can also be given in adjunctive therapy as an alternative drug of choice for anxiety and herpetic neuralgia. Flupenthixol (HCl and decanoate) is primarily indicated in conditions such as depression, muscle spasms of varied etiology, pain, personality disorder, postoperative nausea and vomiting, psychosis, relief of discomfort in mild urinary tract infections, and schizophrenia. Flupenthixol is also seen to possess powerful antibacterial activity both in vitro and in vivo in mouse experiments. It is bacteriostatic in vitro both against gram-positive and gram-negative bacteria. Thiothixene is used in the management of schizophrenia. It has not been evaluated in the management of behavioral complications in patients with mental retardation. Zuclopenthixol is primarily indicated in conditions such as dementia, to enhance permeation of subcutaneous or intramuscular injections, labyrinthine disorders, prolactinoma, psychosis, schizophrenia, and second trimester abortion. It is also used in the treatment of acute bipolar mania.