Dosulepin Explained

Dosulepin, also known as dothiepin and sold under the brand name Prothiaden among others, is a tricyclic antidepressant (TCA) which is used in the treatment of depression.[1] [2] Dosulepin was once the most frequently prescribed antidepressant in the United Kingdom, but it is no longer widely used due to its relatively high toxicity in overdose without therapeutic advantages over other TCAs.[2] [3] [4] It acts as a serotonin–norepinephrine reuptake inhibitor (SNRI) and also has other activities including antihistamine, antiadrenergic, antiserotonergic, anticholinergic, and sodium channel-blocking effects.

Medical uses

Dosulepin is used for the treatment of major depressive disorder.[5] [6] [7] There is clear evidence of the efficacy of dosulepin in psychogenic facial pain, though the drug may be needed for up to a year.[8]

Contraindications

Contraindications include:

Side effects

Common adverse effects:

Less common adverse effects:

Overdose

See main article: Tricyclic antidepressant overdose.

The symptoms and the treatment of an overdose are largely the same as for the other TCAs.[6] Dosulepin may be particularly toxic in overdose compared to other TCAs.[6] The onset of toxic effects is around 4–6 hours after dosulepin is ingested. In order to minimise the risk of overdose it is advised that patients only receive a limited number of tablets at a time so as to limit their risk of overdosing. It is also advised that patients are not prescribed any medications that are known to increase the risk of toxicity in those receiving dosulepin due to the potential for mixed overdoses. The medication should also be kept out of reach of children.

Interactions

Dosulepin can potentiate the effects of alcohol and at least one death has been attributed to this combination. TCAs potentiate the sedative effects of barbiturates, tranquilizers and depressants. Guanethidine and other adrenergic neuron blocking drugs can have their antihypertensive effects blocked by dosulepin. Sympathomimetics may potentiate the sympathomimetic effects of dosulepin. Due to the anticholinergic and antihistamine effects of dosulepin anticholinergic and antihistamine medications may have their effects potentiated by dosulepin and hence these combinations are advised against. Dosulepin may have its postural hypotensive effects potentiated by diuretics. Anticonvulsants may have their efficacy reduced by dosulepin due to its ability to reduce the seizure threshold.

Pharmacology

Pharmacodynamics

See also: Pharmacology of antidepressants.

Dosulepin (and metabolite)[9]
Site Species Ref
8.6–78 192 Human/rat [10] [11]
46–70 25 Human/rat
5,310 2,539 Human/rat
4,004 2,623 Rat [12]
5-HT2A 152 141 Rat
419 950 Rat
2,400 Human [13]
H1 3.6–4 25 Human/rat
25–26 110 Human/rat [14]
  M1 18 Human [15]
  M2 109 Human
  M3 38 Human
  M4 61 Human
  M5 92 Human
Values are Ki (nM). The smaller the value, the more strongly the drug binds to the site.

Dosulepin is a reuptake inhibitor of the serotonin transporter (SERT) and the norepinephrine transporter (NET), thereby acting as an SNRI. It is also an antagonist of the histamine H1 receptor, α1-adrenergic receptor, serotonin 5-HT2 receptors, and muscarinic acetylcholine receptors (mACh), as well as a blocker of voltage-gated sodium channels (VGSCs). The antidepressant effects of dosulepin are thought to be due to inhibition of the reuptake of norepinephrine and possibly also of serotonin.

Dosulepin has three metabolites, northiaden (desmethyldosulepin), dosulepin sulfoxide, and northiaden sulfoxide, which have longer terminal half-lives than that of dosulepin itself. However, whereas northiaden has potent activity similarly to dosulepin, the two sulfoxide metabolites have dramatically reduced activity. They have been described as essentially inactive, and are considered unlikely to contribute to either the therapeutic effects or side effects of dosulepin. Relative to dosulepin, northiaden has reduced activity as a serotonin reuptake inhibitor, antihistamine, and anticholinergic and greater potency as a norepinephrine reuptake inhibitor, similarly to other secondary amine TCAs.[16] [17] Unlike the sulfoxide metabolites, northiaden is thought to play an important role in the effects of dosulepin.

Although Heal & Cheetham (1992) reported relatively high Ki values of 12 and 15 nM for dosulepin and northiaden at the rat α2-adrenergic receptor and suggested that antagonism of the receptor could be involved in the antidepressant effects of dosulepin, Richelson & Nelson (1984) found a low KD of only 2,400 nM for dosulepin at this receptor using human brain tissue. This suggests that it in fact has low potency for this action, similarly to other TCAs.

Pharmacokinetics

Dosulepin is readily absorbed from the small intestine and is extensively metabolized on first-pass through the liver into its chief active metabolite, northiaden. Peak plasma concentrations of between 30.4 and 279 ng/mL (103–944 nmol/L) occur within 2–3 hours of oral administration. It is distributed in breast milk and crosses the placenta and blood–brain barrier. It is highly bound to plasma proteins (84%), and has a whole-body elimination half-life of 51 hours.

Chemistry

Dosulepin is a tricyclic compound, specifically a dibenzothiepine, and possesses three rings fused together with a side chain attached in its chemical structure.[18] It is the only TCA with a dibenzothiepine ring system to have been marketed.[19] The drug is a tertiary amine TCA, with its side chain-demethylated metabolite northiaden (desmethyldosulepin) being a secondary amine.[20] [21] Other tertiary amine TCAs include amitriptyline, imipramine, clomipramine, doxepin, and trimipramine.[22] [23] Dosulepin exhibits (E) and (Z) stereoisomerism like doxepin but in contrast the pure E or trans isomer is used medicinally.[24] [25] The drug is used commercially as the hydrochloride salt; the free base is not used.

History

Dosulepin was developed by SPOFA.[26] It was patented in 1962 and first appeared in the literature in 1962. The drug was first introduced for medical use in 1969, in the United Kingdom.[27]

Society and culture

Generic names

Dosulepin is the English and German generic name of the drug and its and, while dosulepin hydrochloride is its and .[28] [29] [30] [31] Dothiepin is the former of the drug while dothiepin hydrochloride is the former and remains the current . Its generic name in Spanish and Italian and its are dosulepina, in French and its are dosulépine, and in Latin is dosulepinum.

Brand names

Dosulepin is marketed throughout the world mainly under the brand name Prothiaden. It is or has been marketed under a variety of other brand names as well, including Altapin, Depresym, Dopress, Dothapax, Dothep, Idom, Prepadine, Protiaden, Protiadene, Thaden, and Xerenal.

Availability

Dosulepin is marketed throughout Europe (as Prothiaden, Protiaden, and Protiadene), Australia (as Dothep and Prothiaden), New Zealand (as Dopress) and South Africa (as Thaden).[32] [6] [7] It is also available in Japan, Hong Kong, Taiwan, India, Singapore, and Malaysia. The drug is not available in the United States or Canada.

Notes and References

  1. Lancaster SG, Gonzalez JP . Dothiepin. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in depressive illness . Drugs . 38 . 1 . 123–47 . 1989 . 2670509 . 10.2165/00003495-198938010-00005 .
  2. Donovan S, Dearden L, Richardson L . The tolerability of dothiepin: a review of clinical studies between 1963 and 1990 in over 13,000 depressed patients . Prog. Neuropsychopharmacol. Biol. Psychiatry . 18 . 7 . 1143–62 . 1994 . 7846285 . 10.1016/0278-5846(94)90117-1. 29749302 .
  3. Thanacoody HK, Thomas SH . Tricyclic antidepressant poisoning : cardiovascular toxicity . Toxicol Rev . 24 . 3 . 205–14 . 2005 . 16390222 . 10.2165/00139709-200524030-00013. 44532041 .
  4. Gillman PK . Tricyclic antidepressant pharmacology and therapeutic drug interactions updated . Br. J. Pharmacol. . 151 . 6 . 737–48 . 2007 . 17471183 . 2014120 . 10.1038/sj.bjp.0707253 .
  5. Web site: Dothep Dothiepin hydrochloride. TGA eBusiness Services. Alphapharm Pty Limited. 1 November 2013. 3 December 2013. PDF.
  6. Book: Rossi S . 978-0-9805790-9-3 . Australian Medicines Handbook . Adelaide . The Australian Medicines Handbook Unit Trust . 2013 . 2013 .
  7. Book: 978-0-85711-084-8 . British National Formulary (BNF) . Joint Formulary Committee . 2013 . Pharmaceutical Press . London, UK . 65 . registration .
  8. Feinmann C, Harris M, Cawley R . Psychogenic facial pain: presentation and treatment . British Medical Journal . 288 . 6415 . 436–438 . February 1984 . 6419955 . 1444752 . 10.1136/bmj.288.6415.436 .
  9. Web site: PDSP Ki Database . Psychoactive Drug Screening Program (PDSP) . Roth BL, Driscol J . Bryan Roth . University of North Carolina at Chapel Hill and the United States National Institute of Mental Health . 14 August 2017 .
  10. Tatsumi M, Groshan K, Blakely RD, Richelson E . Pharmacological profile of antidepressants and related compounds at human monoamine transporters . European Journal of Pharmacology . 340 . 2–3 . 249–258 . December 1997 . 9537821 . 10.1016/s0014-2999(97)01393-9 .
  11. Heal D, Cheetham S, Martin K, Browning J, Luscombe G, Buckett R . Comparative pharmacology of dothiepin, its metabolites, and other antidepressant drugs. Drug Development Research. 27. 2. 1992. 121–135. 0272-4391. 10.1002/ddr.430270205. 95382318.
  12. Sánchez C, Hyttel J . Comparison of the effects of antidepressants and their metabolites on reuptake of biogenic amines and on receptor binding . Cell. Mol. Neurobiol. . 19 . 4 . 467–89 . 1999 . 10379421 . 10.1023/A:1006986824213. 19490821 .
  13. Richelson E, Nelson A . Antagonism by antidepressants of neurotransmitter receptors of normal human brain in vitro . J. Pharmacol. Exp. Ther. . 230 . 1 . 94–102 . 1984 . 6086881 .
  14. Cusack B, Nelson A, Richelson E . Binding of antidepressants to human brain receptors: focus on newer generation compounds . Psychopharmacology . 114 . 4 . 559–65 . 1994 . 7855217 . 10.1007/bf02244985. 21236268 .
  15. Stanton T, Bolden-Watson C, Cusack B, Richelson E . Antagonism of the five cloned human muscarinic cholinergic receptors expressed in CHO-K1 cells by antidepressants and antihistaminics . Biochem. Pharmacol. . 45 . 11 . 2352–4 . 1993 . 8100134 . 10.1016/0006-2952(93)90211-e.
  16. Book: Hales RE, Yudofsky SC, Gabbard GO . Essentials of Psychiatry. 2011. American Psychiatric Pub. 978-1-58562-933-6. 468–.
  17. Book: Burtis CA, Ashwood ER, Bruns DE . Tietz Textbook of Clinical Chemistry and Molecular Diagnostics - E-Book. 14 October 2012. Elsevier Health Sciences. 978-1-4557-5942-2. 1129–.
  18. Book: Aronson JK . Meyler's Side Effects of Psychiatric Drugs. 2009. Elsevier. 978-0-444-53266-4. 7–.
  19. Book: Ritsner MS . Polypharmacy in Psychiatry Practice, Volume I: Multiple Medication Use Strategies. 15 February 2013. Springer Science & Business Media. 978-94-007-5805-6. 270–271.
  20. Book: Cutler NR, Sramek JJ, Narang PK . Pharmacodynamics and Drug Development: Perspectives in Clinical Pharmacology. 20 September 1994. John Wiley & Sons. 978-0-471-95052-3. 160–.
  21. Book: Anzenbacher P, Zanger UM . Metabolism of Drugs and Other Xenobiotics. 23 February 2012. John Wiley & Sons. 978-3-527-64632-6. 302–.
  22. Book: Anthony PK . Pharmacology Secrets. 2002. Elsevier Health Sciences. 1-56053-470-2. 39–.
  23. Book: Cowen P, Harrison P, Burns T . Shorter Oxford Textbook of Psychiatry. 9 August 2012. OUP Oxford. 978-0-19-162675-3. 532–.
  24. Book: Lemke TL, Williams DA . Foye's Principles of Medicinal Chemistry. 24 January 2012. Lippincott Williams & Wilkins. 978-1-60913-345-0. 607–.
  25. Book: Psychotropic Agents: Part I: Antipsychotics and Antidepressants. 6 December 2012. Springer Science & Business Media. 978-3-642-67538-6. 354–.
  26. Andersen J, Kristensen AS, Bang-Andersen B, Strømgaard K . Recent advances in the understanding of the interaction of antidepressant drugs with serotonin and norepinephrine transporters . Chem. Commun. . 25 . 3677–92 . 2009 . 19557250 . 10.1039/b903035m .
  27. Book: Dart RC . Medical Toxicology. 2004. Lippincott Williams & Wilkins. 978-0-7817-2845-4. 836–.
  28. Book: Elks J . The Dictionary of Drugs: Chemical Data: Chemical Data, Structures and Bibliographies. 14 November 2014. Springer. 978-1-4757-2085-3. 468–.
  29. Book: Index Nominum 2000: International Drug Directory. 2000. Taylor & Francis. 978-3-88763-075-1. 369–.
  30. Book: Morton IK, Hall JM . Concise Dictionary of Pharmacological Agents: Properties and Synonyms. 6 December 2012. Springer Science & Business Media. 978-94-011-4439-1. 105–.
  31. Web site: Dosulepin.
  32. Book: Dosulepin Hydrochloride. Martindale: The Complete Drug Reference. 5 December 2011. 15 August 2017. Pharmaceutical Press. London, UK.

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