Cor Vasa 2002, 43(6):276-280
Therapeutic drug monitoring (TDM) and serum levels of digoxin: Is the so-called "therapeutic range" indeed evidence based?
- Pracoviště klinické farmakologie, Institut klinické a experimentální medicíny, Praha, Česká republika
Background:
Digoxin is among the most frequently prescribed medications in the treatment of cardiovascular diseases. The narrow margin between toxic and non-toxic serum digoxin concentrations, coupled with substantial variability among patients, has led to the routine use of serum digoxin concentration to guide therapy. Although the monitoring of serum digoxin concentrations may be a valuable tool, its appropriate use remains an important concern.
Purpose:
This study was priory to assess the significance of therapeutic drug monitoring on optimizing digoxin therapy and the role of digoxin serum assays in patient care.
Setting:
Institute for Clinical and Experimental Medicine, Department of clinical pharmacology with facilities for therapeutic drug monitoring.
Design:
Retrospective data analysis of one-year period for digoxin serum levels.
Methods:
Serum digoxin levels of 100 heterogeneous patients previously analyzed by FPIA-Abbott TDx and MW/Pharm pharmacokinetic programs were retrospectively (1 year period) analyzed to assess impact of therapeutic digoxin monitoring on further treatment.
Results:
Only 29% of the subjects on long-term digoxin maintenance doses showed serum digoxin levels within published therapeutic ranges. Digoxin withdraw was warranted in 13% of cases due to levels showing probability to toxicity, despite absence of typical symptoms. Surprisingly 58% of the subjects had levels below 0.8 ng/mL (published therapeutic range).
Conclusion:
This observation suggests that unexpectedly high or low serum digoxin levels should be viewed with initial skepticism in a patient with adequate disease control and no signs or symptoms of digoxin toxicity confirming the adage "do not treat the number, treat the patient", which holds true for digoxin serum assay results.
Keywords: Serum digoxin levels; Cardiotoxicity; Therapeutic drug monitoring
Published: June 1, 2002 Show citation