chemists to explore phenothiazine derivatives and their activity was a pioneering example of medicinal chemistry; phenothiazine is often discussed as a prototypical example of a pharmaceutical lead structure. A number of phenothiazines other than methylene blue have been shown to have antimicrobial effects. In particular, thioridazine has been shown to make extensively drug-resistant tuberculosis (XDR-TB) drug-susceptible again and make methicillin-resistant Staphylococcus aureus (MRSA) susceptible to beta-lactam antibiotics. The major reason why thioridazine has not been utilized as an antimicrobial agent (it is a first-generation or "typical" antipsychotic medication) is due to its adverse effects on the central nervous system and cardiovascular system (particularly QT interval prolongation). The term "phenothiazines" describes the largest of the five main classes of antipsychotic drugs. These drugs have antipsychotic and, often, antiemetic properties, although they may also cause severe side effects such as extrapyramidal symptoms (including akathisia and tardive dyskinesia), hyperprolactinaemia, and the rare but potentially fatal neuroleptic malignant syndrome, as well as substantial weight gain. Use of phenothiazines has been associated with antiphospholipid syndrome, but no causal relationship has been established. Phenothiazine antipsychotics are classified into three groups that differ with respect to the substituent on nitrogen: the aliphatic compounds (bearing acyclic groups), the "piperidines" (bearing piperidine-derived groups), and the piperazine (bearing piperazine-derived substituents). Nondrug applications The synthetic dye methylene blue, containing the structure, was described in 1876. Many water-soluble phenothiazine derivatives, such as methylene blue, methylene green, thionine, and others, can be electropolymerized into conductive polymers used as electrocatalysts for NADH oxidation in enzymatic biosensors and biofuel cells. Phenothiazine is used as an anaerobic inhibitor for acrylic acid polymerization, often used as an in-process inhibitor during the purification of acrylic acid. Trade names Like many commercially significant compounds, phenothiazine has numerous trade names, including AFI-Tiazin, Agrazine, Antiverm, Biverm, Dibenzothiazine, Orimon, Lethelmin, Souframine, Nemazene, Vermitin, Padophene, Fenoverm, Fentiazine, Contaverm, Fenothiazine, Phenovarm, Ieeno, ENT 38, Helmetina, Helmetine, Penthazine, XL-50, Wurm-thional, Phenegic, Phenovis, Phenoxur, and Reconox. Former uses Phenothiazine was formerly used as an insecticide and as a drug to treat infections with parasitic worms (anthelminthic) in livestock and people, but its use for those purposes has been superseded by other chemicals. Phenothiazine was introduced by DuPont as an insecticide in 1935. About 3,500,000 pounds were sold in the US in 1944. However, because it was degraded by sunlight and air, it was difficult to determine how much to use in the field, and its use