Thioridazine
Clinical data
AHFS/Drugs.comProfessional Drug Facts
MedlinePlusa682119
License data
Pregnancy
category
  • AU: C
Routes of
administration		Oral
Drug classTypical antipsychotic
ATC code
Legal status
Legal status
  • BR: Class C1 (Other controlled substances)[1]
  • Withdrawn by the manufacturer worldwide;[2] generic formulations are still available by prescription
Pharmacokinetic data
BioavailabilityIncomplete
MetabolismHepatic (at least partly mediated by CYP2D6)
Elimination half-life21–24 hours[3]
ExcretionFeces
Identifiers
  • 10-{2-[(RS)-1-Methylpiperidin-2-yl]ethyl}-
    2-methylsulfanylphenothiazine
CAS Number
PubChem CID
PubChem SID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.000.041
Chemical and physical data
FormulaC21H26N2S2
Molar mass370.57 g·mol−1
3D model (JSmol)
  • S(c2cc1N(c3c(Sc1cc2)cccc3)CCC4N(C)CCCC4)C
  • InChI=1S/C21H26N2S2/c1-22-13-6-5-7-16(22)12-14-23-18-8-3-4-9-20(18)25-21-11-10-17(24-2)15-19(21)23/h3-4,8-11,15-16H,5-7,12-14H2,1-2H3 checkY
  • Key:KLBQZWRITKRQQV-UHFFFAOYSA-N checkY
  (verify)

Thioridazine (Mellaril or Melleril) is a first generation antipsychotic drug 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 The branded product was withdrawn worldwide in 2005 because it caused severe cardiac arrhythmias.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]

Indications

Thioridazine was voluntarily discontinued by its manufacturer, Novartis, worldwide because it caused severe cardiac arrhythmias however generics remain on the market..[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 its restricted to patients who have taken at least 2 other antipsychotics that either failed or caused serious side effects [10]

Side effects

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]

Biologic ProteinBinding affinity (Ki[nM])Binding affinity of Mesoridazine (Ki [nM])Binding affinity of Sulforidazine (Ki [nM])Notes
SERT1259NDND
NET842NDND
DAT1684NDND
5-HT1A144.35500 (HB)ND
5-HT1B109NDND
5-HT1D579NDND
5-HT1E194NDND
5-HT2A27.674.76 (HB)NDThe 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]
5-HT2C53157NDBelieved to play a role in the weight gain-promoting effects of antipsychotics.[7]
5-HT3>10000NDND
5-HT5A364NDND
5-HT657.05380ND
5-HT79973 (RC)ND
α1A3.152 (HB)NDLikely the receptor responsible for the orthostatic hypotension known to occur in individuals on thioridazine.[7]
α1B2.4NDND
α2A134.151612.9 (HB)ND
α2B341.65NDND
α2C74.9NDND
β1>10000NDND
β2>10000NDND
M112.810NDThis 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]
M2286.3315ND
M32990ND
M4310.3319ND
M512.6760ND
D194.5NDND
D20.44.30.25Believed to be the receptor responsible for the therapeutic effects of antipsychotics.[7]
D31.52.60.7
D41.59.1ND
D5258NDND
hERG191NDNDLikely involved in thioridazine's cardiac effects.
H116.51.81 (HB)NDLikely responsible for the sedating effects of thioridazine.
H2136NDNDRegulates the release of hydrochloric acid into the stomach.
H42400NDND

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]

Antibiotic activity

Thioridazine is known to kill extensively drug-resistant tuberculosis[25][26] and to make methicillin-resistant Staphylococcus aureus sensitive to β-lactam antibiotics.[27][28] A possible mechanism of action for the drug's antibiotic activity is via the inhibition of bacterial secretion pumps. The β-lactam antibiotic resistance is due to the secretion β-lactamase a protein that destroys antibiotics. If the bacteria cannot secrete the β-lactamase, then the antibiotic will be effective.[26] The drug has been successfully used in the treatment of granulomatous amoebic encephalitis in conjunction with more conventional amoebicidal medications.

Synthesis

Note: Same sidechain used for mesoridazine and sulforidazine.

Thieme Synthesis:[29] Patent:[30] Sidechain:[31] Enantiomers:[32]

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).

References

  1. ↑ Anvisa (31 March 2023). "RDC Nº 784 - Listas de Substâncias Entorpecentes, Psicotrópicas, Precursoras e Outras sob Controle Especial" [Collegiate Board Resolution No. 784 - Lists of Narcotic, Psychotropic, Precursor, and Other Substances under Special Control] (in Brazilian Portuguese). Diário Oficial da União (published 4 April 2023). Archived from the original on 3 August 2023. Retrieved 16 August 2023.
  2. 1 2 3 4 "SHARED CARE PROTOCOL Thioridazine" (PDF). NHS Lothian Joint Formulary. March 2012. Archived from the original (PDF) on 18 May 2015.
  3. ↑ 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. PMID 6470190. S2CID 33161119.
  4. 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. PMID 22941581. S2CID 19560432.
  5. ↑ "WHO Pharmaceuticals Newsletter 2005, No. 04: REGULATORY MATTERS: Thioridazine - Sale discontinued in Canada". Essential Medicines and Health Products Information Portal. Vol. 4, no. 2. World Health Organization. 2005. p. 5. Archived from the original on 28 May 2011. Retrieved 28 October 2013.
  6. ↑ "Withdrawal of thioridazine" (PDF). Australian Prescriber. Vol. 30, no. 3. June 2007. p. 82.
  7. 1 2 3 4 5 6 Brunton LL, Chabner B, Knollmann BC, eds. (2011). Goodman & Gilman's The Pharmacological Basis of Therapeutics (12th ed.). New York: McGraw-Hill. ISBN 978-0-07-162442-8.
  8. ↑ Kirchner V, Kelly CA, Harvey RJ (2001). "Thioridazine for dementia". The Cochrane Database of Systematic Reviews (3): CD000464. doi:10.1002/14651858.CD000464. PMC 7034526. PMID 11686961.
  9. ↑ 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. PMID 23543555.
  10. ↑ "Thioridazine: MedlinePlus Drug Information". medlineplus.gov. Retrieved 7 June 2023.
  11. 1 2 3 "THIORIDAZINE HYDROCHLORIDE tablet, film coated [Mutual Pharmaceutical]". DailyMed. Mutual Pharmaceutical. September 2010. Retrieved 28 October 2013.
  12. ↑ Fenton M, Rathbone J, Reilly J, Sultana A (July 2007). "Thioridazine for schizophrenia". The Cochrane Database of Systematic Reviews. 2007 (3): CD001944. doi:10.1002/14651858.CD001944.pub2. PMC 6718212. PMID 17636691.
  13. ↑ Keks N, McGrath J, Lambert T, Catts S, Vaddadi K, Burrows G, et al. (November 1994). "The Australian multicentre double-blind comparative study of remoxipride and thioridazine in schizophrenia". Acta Psychiatrica Scandinavica. 90 (5): 358–365. doi:10.1111/j.1600-0447.1994.tb01607.x. PMID 7872041. S2CID 40042606.
  14. ↑ Fornaro P, Calabria G, Corallo G, Picotti GB (July 2002). "Pathogenesis of degenerative retinopathies induced by thioridazine and other antipsychotics: a dopamine hypothesis". Documenta Ophthalmologica. Advances in Ophthalmology. 105 (1): 41–49. doi:10.1023/A:1015768114192. PMID 12152801. S2CID 23618581.
  15. ↑ "Martindale: The Complete Drug Reference". Medicines Complete. The Pharmaceutical Press. 18 August 2010. Retrieved 28 October 2013.
  16. ↑ "Selected adverse effects of antipsychotic medications for schizophrenia". UpToDate. Wolters Kluwer Health. Retrieved 24 October 2013.
  17. ↑ Scott AW (December 1963). "Retinal Pigmentation in a Patient Receiving Thioridazine". Archives of Ophthalmology. 70 (6): 775–778. doi:10.1001/archopht.1963.00960050777009. PMID 14065014.
  18. ↑ "Thioridazine". LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. National Institute of Diabetes and Digestive and Kidney Diseases. 2012. PMID 31643669.
  19. ↑ 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.
  20. ↑ PubChem Substance Summary: Mesoridazine National Center for Biotechnology Information.
  21. ↑ 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. PMID 8653995. S2CID 45135063.
  22. ↑ PubChem Substance Summary: Sulforidazine National Center for Biotechnology Information.
  23. ↑ Daniel WA, Syrek M, Ryłko Z, Kot M (2001). "Effects of phenothiazine neuroleptics on the rate of caffeine demethylation and hydroxylation in the rat liver" (PDF). Polish Journal of Pharmacology. 53 (6): 615–621. PMID 11985335.
  24. ↑ "Thioridazine: MedlinePlus Drug Information". medlineplus.gov. Retrieved 7 June 2023.
  25. ↑ Amaral L, Boeree MJ, Gillespie SH, Udwadia ZF, van Soolingen D (June 2010). "Thioridazine cures extensively drug-resistant tuberculosis (XDR-TB) and the need for global trials is now!" (PDF). International Journal of Antimicrobial Agents. 35 (6): 524–526. doi:10.1016/j.ijantimicag.2009.12.019. PMID 20188526.
  26. 1 2 Amaral L, Viveiros M (May 2012). "Why thioridazine in combination with antibiotics cures extensively drug-resistant Mycobacterium tuberculosis infections". International Journal of Antimicrobial Agents. 39 (5): 376–380. doi:10.1016/j.ijantimicag.2012.01.012. PMID 22445204.
  27. ↑ Thanacoody HK (November 2007). "Thioridazine: resurrection as an antimicrobial agent?". British Journal of Clinical Pharmacology. 64 (5): 566–574. doi:10.1111/j.1365-2125.2007.03021.x. PMC 2203271. PMID 17764469.
  28. ↑ Thorsing M, Klitgaard JK, Atilano ML, Skov MN, Kolmos HJ, Filipe SR, Kallipolitis BH (May 2013). "Thioridazine induces major changes in global gene expression and cell wall composition in methicillin-resistant Staphylococcus aureus USA300". PLOS ONE. 8 (5): e64518. Bibcode:2013PLoSO...864518T. doi:10.1371/journal.pone.0064518. PMC 3656896. PMID 23691239.
  29. ↑ Bourquin JP, Schwarb G, Gamboni G, Fischer R, Ruesch L, Guldimann S, Theus V, Schenker E, Renz J (1958). "Synthesen auf dem Phenothiazin-Gebiet. 2. Mitteilung. N-substituierte Mercaptophenothiazin-Derivate". Helvetica Chimica Acta. 41 (4): 1072–1108. doi:10.1002/hlca.19580410420.
  30. ↑ US 3239514, Renz J, Bourquin JP, "Phenothiazine derivatives substituted by a monovalent sulfur function in 3-position", issued 1966, assigned to Sandoz KK
  31. ↑ 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. PMID 20994984.
  32. ↑ Antonsen SG, Monsen EB, Ovchinnikov K, Nolsøe JM, Ekeberg D, Kristiansen JE, Diep DB, Stenstrøm YH (2020). "Synthesis of the enantiomers of thioridazine". SynOpen. 4 (1): 12–16. doi:10.1055/s-0039-1690834.

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