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


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Debbie Pelser

Medical Department Manager, Lundbeck Australia Baulkham Hills, NSW

Andrew Somogyi

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