Australian Prescriber An independent Review Logo
ISSUE 5 OCTOBER
Letters to the Editor

Therapeutic range for digoxin

  • John D Horowitz, Dr Ghiculescu

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.

 

Letter to the Editor

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

 

Author's comments

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.

 

References

  1. The Digitalis Investigation Group. The effect of digoxin on mortality and morbidity in patients with heart failure. N Engl J Med 1997;336:525-33.
  2. Ahmed A, Rich MW, Love TE, Lloyd-Jones DM, Aban IB, Colucci WS, et al. Digoxin and reduction in mortality and hospitalization in heart failure: a comprehensive post hoc analysis of the DIG trial. Eur Heart J 2006;27:178-86.
  3. Chatterjee K. Congestive heart failure: what should be the initial therapy and why? Am J Cardiovasc Drugs 2002;2:1-6.

John D Horowitz

Head of Cardiology, The University of Adelaide

Dr Ghiculescu