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Thioridazine (Mellaril or Melleril) is a first generation antipsychoticdrug belonging to the phenothiazine drug group and was previously widely used in the treatment of schizophrenia and psychosis. The branded product was withdrawn worldwide in 2005 because it caused severe cardiac arrhythmias. However, generic versions are still available in the US.[2]
Thioridazine was voluntarily discontinued by its manufacturer, Novartis, worldwide because it caused severe cardiac arrhythmias. However, generics remain on the market in some countries.[2][4][5][6]
Its primary use in medicine is for the treatment of schizophrenia.[7] It was also tried with some success as a treatment for various psychiatric symptoms seen in people with dementia,[8] but chronic use of thioridazine and other anti-psychotics in people with dementia is not recommended.[9] Generic forms of thioridazine remain on the market in a few countries, usually with restrictions due to the risk of arrhythmias. For example, in the US, it is restricted to patients who have taken at least 2 other antipsychotics that either failed or caused serious side effects. [10]
Thioridazine prolongs the QTc interval in a dose-dependent manner.[11] It produces significantly less extrapyramidal side effects than most first-generation antipsychotics, likely due to its potent anticholinergic effect.[12][13] Its use, along with the use of other typical antipsychotics, has been associated with degenerative retinopathies (specifically retinitis pigmentosa).[14] It has a higher propensity for causing anticholinergic side effects coupled with a lower propensity for causing extrapyramidal side effects and sedation than chlorpromazine, but also has a higher incidence of hypotension and cardiotoxicity.[15] It is also known to possess a relatively high liability for causing orthostatic hypotension compared to other antipsychotics. Similarly to other first-generation antipsychotics it has a relatively high liability for causing prolactin elevation. It is moderate risk for causing weight gain.[16] As with all antipsychotics thioridazine has been linked to cases of tardive dyskinesia (an often permanent neurological disorder characterised by slow, repetitive, purposeless and involuntary movements, most often of the facial muscles, that is usually brought on by years of continued treatment with antipsychotics, especially the first-generation (or typical) antipsychotics such as thioridazine) and neuroleptic malignant syndrome (a potentially fatal complication of antipsychotic treatment).[11] Blood dyscrasias such as agranulocytosis, leukopenia and neutropenia are possible with thioridazine treatment.[11] Thioridazine is also associated with abnormal retinal pigmentation after many years of use.[17] Thioridazine has been correlated to rare instances of clinically apparent acute cholestatic liver injury. [18]
Pharmacology
Thioridazine has the following binding profile:[19]
The ratio of 5-HT2A to D2 receptor binding is believed to dictate whether or not most antipsychotics are atypical or typical. In thioridazine's case its ratio of 5-HT2A to D2 receptor binding is below the level that's believed to be required for atypicality despite its relatively low extrapyramidal side effect liability in practice.[7]
This receptor is believed to be the chief receptor responsible for the anticholinergic side effects of thioridazine (e.g. dry mouth, constipation, blurred vision, etc.). Likely plays a role in thioridazine's low extrapyramidal side effect liability as anticholinergic drugs such as benzatropine are routinely given to treat extrapyramidal side effects resulting from antipsychotic treatment.[7]
Note: The Binding affinities given are towards cloned human receptors unless otherwise specified
Acronyms used HB – Human brain receptor RC – Cloned rat receptor ND – No data
Metabolism
Thioridazine is a racemic compound with two enantiomers, both of which are metabolized, according to Eap et al., by CYP2D6 into (S)- and (R)-thioridazine-2-sulfoxide, better known as mesoridazine,[20] and into (S)- and (R)-thioridazine-5-sulfoxide.[21] Mesoridazine is in turn metabolized into sulforidazine.[22] Thioridazine is an inhibitor of CYP1A2 and CYP3A4.[23]
History
The manufacturer Novartis/Sandoz/Wander of the brands of thioridazine, Mellaril in the US and Canada and Melleril in Europe, discontinued the drug worldwide in June 2005.[2][4]
Generic forms of thioridazine however remain on the market in a few countries usually with restrictions for example in the US its restricted to patients who have taken at least 2 other antipsychotics that either failed or caused serious side effects [24]
The alkylation of 2-Picoline [109-06-8] (1) with formaldehyde gives 2-Pyridineethanol [103-74-2] (2). Forming the quat salt with methyl iodide [74-88-4] leads to 2-(2-hydroxyethyl)-1-methyl-pyridinium iodide [56622-15-2] (3). Catalytic hydrogenation in the presence of hydrochloric acid leads to 2-(2-Chloroethyl)-1-Methylpiperidine [50846-01-0] (4). Alkylation of 2-Methylthiophenothiazine [7643-08-5] (5) in the presence of sodium hydride base completed the synthesis of Thioridazine (6).
Related Research Articles
Antipsychotics, previously known as neuroleptics and major tranquilizers, are a class of psychotropic medication primarily used to manage psychosis, principally in schizophrenia but also in a range of other psychotic disorders. They are also the mainstay, together with mood stabilizers, in the treatment of bipolar disorder. Moreover, they are also used as adjuncts in the treatment of treatment-resistant major depressive disorder.
Phenothiazine, abbreviated PTZ, is an organic compound that has the formula S(C6H4)2NH and is related to the thiazine-class of heterocyclic compounds. Derivatives of phenothiazine are highly bioactive and have widespread use and rich history.
Neuroleptic malignant syndrome (NMS) is a rare but life-threatening reaction that can occur in response to antipsychotic (neuroleptic) medications. Symptoms include high fever, confusion, rigid muscles, variable blood pressure, sweating, and fast heart rate. Complications may include rhabdomyolysis, high blood potassium, kidney failure, or seizures.
Trifluoperazine, marketed under the brand name Stelazine among others, is a typical antipsychotic primarily used to treat schizophrenia. It may also be used short term in those with generalized anxiety disorder but is less preferred to benzodiazepines. It is of the phenothiazine chemical class. It was approved for medical use in the United States in 1959.
Chlorpromazine (CPZ), marketed under the brand names Thorazine and Largactil among others, is an antipsychotic medication. It is primarily used to treat psychotic disorders such as schizophrenia. Other uses include the treatment of bipolar disorder, severe behavioral problems in children including those with attention deficit hyperactivity disorder, nausea and vomiting, anxiety before surgery, and hiccups that do not improve following other measures. It can be given orally, by intramuscular injection, or intravenously.
Fluphenazine, sold under the brand name Prolixin among others, is a high-potency typical antipsychotic medication. It is used in the treatment of chronic psychoses such as schizophrenia, and appears to be about equal in effectiveness to low-potency antipsychotics like chlorpromazine. It is given by mouth, injection into a muscle, or just under the skin. There is also a long acting injectable version that may last for up to four weeks. Fluphenazine decanoate, the depot injection form of fluphenazine, should not be used by people with severe depression.
Typical antipsychotics are a class of antipsychotic drugs first developed in the 1950s and used to treat psychosis. Typical antipsychotics may also be used for the treatment of acute mania, agitation, and other conditions. The first typical antipsychotics to come into medical use were the phenothiazines, namely chlorpromazine which was discovered serendipitously. Another prominent grouping of antipsychotics are the butyrophenones, an example of which is haloperidol. The newer, second-generation antipsychotics, also known as atypical antipsychotics, have largely supplanted the use of typical antipsychotics as first-line agents due to the higher risk of movement disorders in the latter.
The atypical antipsychotics (AAP), also known as second generation antipsychotics (SGAs) and serotonin–dopamine antagonists (SDAs), are a group of antipsychotic drugs largely introduced after the 1970s and used to treat psychiatric conditions. Some atypical antipsychotics have received regulatory approval for schizophrenia, bipolar disorder, irritability in autism, and as an adjunct in major depressive disorder.
Risperidone, sold under the brand name Risperdal among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder. It is taken either by mouth or by injection. The injectable versions are long-acting and last for 2–4 weeks.
Perphenazine is a typical antipsychotic drug. Chemically, it is classified as a piperazinyl phenothiazine. Originally marketed in the United States as Trilafon, it has been in clinical use for decades.
Prochlorperazine, formerly sold under the brand name Compazine among others, is a medication used to treat nausea, migraines, schizophrenia, psychosis and anxiety. It is a less preferred medication for anxiety. It may be taken by mouth, rectally, injection into a vein, or injection into a muscle.
Sulforidazine a typical antipsychotic and a metabolite of thioridazine; it and mesoridazine are more potent than the parent compound, whose pharmacological effects are believed by some to be largely due to its metabolism into sulforidazine and mesoridazine.
Amisulpride is an antiemetic and antipsychotic medication used at lower doses intravenously to prevent and treat postoperative nausea and vomiting; and at higher doses by mouth to treat schizophrenia and acute psychotic episodes. It is sold under the brand names Barhemsys and Solian, Socian, Deniban and others. At very low doses it is also used to treat dysthymia.
Sulpiride, sold under the brand name Dogmatil among others, is an atypical antipsychotic medication of the benzamide class which is used mainly in the treatment of psychosis associated with schizophrenia and major depressive disorder, and sometimes used in low dosage to treat anxiety and mild depression. Sulpiride is commonly used in Asia, Central America, Europe, South Africa and South America. Levosulpiride is its purified levo-isomer and is sold in India for similar purpose. It is not approved in the United States, Canada, or Australia. The drug is chemically and clinically similar to amisulpride.
Mesoridazine(Serentil) is a piperidine neuroleptic drug belonging to the class of drugs called phenothiazines, used in the treatment of schizophrenia. It is a metabolite of thioridazine. The drug's name is derived from the methylsulfoxy and piperidine functional groups in its chemical structure.
Melperone is an atypical antipsychotic of the butyrophenone chemical class, making it structurally related to the typical antipsychotic haloperidol. It first entered clinical use in 1960s.
Cyamemazine (Tercian), also known as cyamepromazine, is a typical antipsychotic drug of the phenothiazine class which was introduced by Theraplix in France in 1972 and later in Portugal as well.
Pipotiazine (Piportil), also known as pipothiazine, is a typical antipsychotic of the phenothiazine class used in the United Kingdom and other countries for the treatment of schizophrenia. Its properties are similar to those of chlorpromazine. A 2004 systematic review investigated its efficacy for people with schizophrenia:
Clotiapine (Entumine) is an atypical antipsychotic of the dibenzothiazepine chemical class. It was first introduced in a few European countries, Argentina, Taiwan and Israel in 1970.
↑ Shvartsburd A, Sajadi C, Morton V, Mirabi M, Gordon J, Smith RC (August 1984). "Blood levels of haloperidol and thioridazine during maintenance neuroleptic treatment of schizophrenic outpatients". Journal of Clinical Psychopharmacology. 4 (4): 194–198. doi:10.1097/00004714-198408000-00004. PMID6470190. S2CID33161119.
1 2 Purhonen M, Koponen H, Tiihonen J, Tanskanen A (November 2012). "Outcome of patients after market withdrawal of thioridazine: a retrospective analysis in a nationwide cohort". Pharmacoepidemiology and Drug Safety. 21 (11): 1227–1231. doi:10.1002/pds.3346. PMID22941581. S2CID19560432.
↑ Declercq T, Petrovic M, Azermai M, Vander Stichele R, De Sutter AI, van Driel ML, Christiaens T (March 2013). "Withdrawal versus continuation of chronic antipsychotic drugs for behavioural and psychological symptoms in older people with dementia". The Cochrane Database of Systematic Reviews. 3 (3): CD007726. doi:10.1002/14651858.CD007726.pub2. hdl:1854/LU-3109108. PMID23543555.
↑ "Thioridazine". LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. National Institute of Diabetes and Digestive and Kidney Diseases. 2012. PMID31643669.
↑ Roth BL, Driscol J (12 January 2011). "PDSP Ki Database". Psychoactive Drug Screening Program (PDSP). University of North Carolina at Chapel Hill and the United States National Institute of Mental Health. Archived from the original on 8 November 2013. Retrieved 28 October 2013.
↑ Eap CB, Guentert TW, Schãublin-Loidl M, Stabl M, Koeb L, Powell K, Baumann P (March 1996). "Plasma levels of the enantiomers of thioridazine, thioridazine 2-sulfoxide, thioridazine 2-sulfone, and thioridazine 5-sulfoxide in poor and extensive metabolizers of dextromethorphan and mephenytoin". Clinical Pharmacology and Therapeutics. 59 (3): 322–331. doi:10.1016/S0009-9236(96)80010-5. PMID8653995. S2CID45135063.
↑ US 3239514,Renz J, Bourquin JP,"Phenothiazine derivatives substituted by a monovalent sulfur function in 3-position",issued 1966, assigned to Sandoz KK
↑ Norton TR, Seibert RA, Benson AA, Bergstrom FW (August 1946). "The synthesis of some substituted 8-aminoquinolines". Journal of the American Chemical Society. 68 (8): 1572–6. doi:10.1021/ja01212a058. PMID20994984.
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