Letters to the Editor
Therapeutic range for digoxin
- John D Horowitz, Dr Ghiculescu
- Aust Prescr 2008;31:115-8
- 1 October 2008
- DOI: 10.18773/austprescr.2008.066
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Editor, I read with great interest the target ranges for digoxin interactions in Table 1 of the article on therapeutic drug monitoring (Aust Prescr 2008;31:42-4). The issue of the therapeutic range for digoxin is perhaps a controversial one these days, but the author should certainly be given an opportunity to explain the 'range', particularly because of recent analyses of mortality data in trials of digoxin.
Perhaps a suitable correction as well as clarification would be in order?
John D Horowitz
Head of Cardiology
The University of Adelaide
Dr Ghiculescu, author of the article, comments:
The Digitalis Investigation Group found that digoxin reduced hospitalisations, but did not reduce overall mortality in heart failure when the target for the therapeutic range was 0.5-2 nanogram/mL.1Post hoc analysis of this trial found that mortality and hospitalisations were reduced if the serum digoxin was 0.5-0.9 nanogram/mL. Concentrations greater than 1 nanogram/mL were associated with higher mortality.2A concentration less than 1 nanogram/mL equates to less than 1 microgram/L. The currently recommended therapeutic range is therefore 0.5-0.9 nanogram/mL.
It has been suggested that an even lower concentration, less than 1 nanogram/dL, be used in patients with symptomatic systolic left ventricular failure.3That equates to 10 nanogram/L which is 0.01 microgram/L. This is significantly lower than the range used in the digoxin trial. However, this low concentration cannot easily be measured.
Head of Cardiology, The University of Adelaide