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ISSUE 5 OCTOBER
Letters to the Editor

Inside the isomers: the tale of chiral switches

  • Debbie Pelser, Andrew Somogyi

Letter to the editor

Editor, – Reference is made to the article 'Inside the isomers: the tale of chiral switches' (Aust Prescr 2004;27:109-13). In this article it is asserted that &aos;in overdose, there is a concern about the potential for sudden death, possibly related to QT prolongation due to a secondary metabolite formed from (R)-citalopram. (S)-citalopram (escitalopram) was therefore developed with the aim of a better harm: benefit ratio compared to (R)-citalopram'. 

Significantly, the authors of this article have not referenced any of the statements in this paragraph. I would like to advise that the statement regarding the propensity of a metabolite of the (R)-enantiomer of citalopram to cause sudden death as a result of QT prolongation is completely unfounded.

A survey has investigated the effects of citalopram, at therapeutic doses, on ECG parameters.1 The authors concluded that citalopram has no significant effects on PQ, QRS or QTc intervals, during short-or long-term treatment. Nor were there any deaths or clinically significant arrhythmias reported among all pure citalopram intoxications (n=108 with doses up to 5.2 g) over a two-year period in Sweden.2

Since there is absolutely no basis to the assertion that a metabolite of (R)-citalopram is associated with sudden death as a result of QT prolongation, the reason given for the development of (S)-citalopram is also purely speculative and quite simply, untrue.

Debbie Pelser
Medical Department Manager
Lundbeck Australia
Baulkham Hills, NSW

 

Author's comment

Associate Professor Andrew Somogyi, one of the authors of the article, comments:

There is evidence that the didesmethyl metabolite of (R)-citalopram prolongs the QT interval in animals and therefore might contribute to those rare instances of cardiac arrhythmia after very high doses of citalopram in a suicidal setting.3,4,5,6

 

References

  1. Rasmussen SL, Overo KF, Tanghoj P. Cardiac safety of citalopram: prospective trials and retrospective analyses. J Clin Pyschopharmacol 1999;19:407-15.
  2. Personne M, Persson H, Sjoberg G. Citalopram toxicity [letter]. Lancet 1997;350:518-9.
  3. Ostrom M, Eriksson A, Thorson J, Spigset O. Fatal overdose with citalopram [letter]. Lancet 1996;348:339-40.
  4. Catalano G, Catalano MC, Epstein MA, Tsambiras PE. QTc interval prolongation associated with citalopram overdose: a case report and literature review. Clin Neuropharmacol 2001;24:158-62.
  5. Eichelbaum M, Testa B, Somogyi A, editors. Stereochemical aspects of drug action and disposition. Handbook of Experimental Pharmacology, Vol 153. Berlin, New York: Springer; 2003.
  6. Meuleman C, Jourdain P, Bellorini M, Sadeg N, Loiret J, Guillard N, et al. [Citalopram and torsades de pointes. A case report] [French]. Arch Mal Coeur Vaiss 2001;94:1021-4.
 

The Editorial Executive Committee welcomes letters, which should be less than 250 words. Before a decision to publish is made, letters which refer to a published article may be sent to the author for a response. Any letter may be sent to an expert for comment. When letters are published, they are usually accompanied in the same issue by their responses or comments. The Committee screens out discourteous, inaccurate or libellous statements. The letters are sub-edited before publication. Authors are required to declare any conflicts of interest. The Committee's decision on publication is final.

RELATED ARTICLES
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Isomers - correction Aust Prescr 2005;28:55-8
Experimental and Clinical Pharmacology
Inside the isomers: the tale of chiral switches Aust Prescr 2004;27:109-13
RELATED ARTICLES
Letters to the Editor
Isomers - correction Aust Prescr 2005;28:55-8
Experimental and Clinical Pharmacology
Inside the isomers: the tale of chiral switches Aust Prescr 2004;27:109-13

Debbie Pelser

Medical Department Manager, Lundbeck Australia Baulkham Hills, NSW

Andrew Somogyi

Department of Clinical and Experimental Pharmacology, University of Adelaide, Adelaide