Sensitive and specific LC-MS assay for quantification of digoxin in human plasma and urine

Biomed Chromatogr. 2008 Jul;22(7):712-8. doi: 10.1002/bmc.988.


Digoxin, a commonly prescribed cardiac glycoside with a narrow therapeutic window, is routinely used in pharmacokinetic studies to assess the in vivo activity of the drug efflux pump P-glycoprotein. To minimize adverse events, a sub-therapeutic dose of digoxin is usually administered, producing low plasma concentrations requiring a sensitive detection technique. Commonly available immunoassay techniques do not provide the required sensitivity to measure these low plasma concentrations and are potentially non-specific in certain subject populations. Previously published mass spectrometric techniques require either large plasma volumes or a tandem mass spectrometer. To overcome these challenges we have developed a sensitive and specific LC-MS method for the quantification of digoxin in small volumes of human plasma and urine. Plasma (1 mL) was extracted with methyl t-butyl ether under basic conditions followed by LC-MS detection of the sodium adducts of digoxin (803.4 m/z) and digitoxin (787.4 m/z, internal standard). Linearity and accuracy were demonstrated across a wide range of digoxin plasma concentration (0.05-1.5 ng/mL). This specific, sensitive, validated digoxin LC-MS assay can be used to quantify sub-therapeutic digoxin plasma concentrations in men and women (pregnant and non-pregnant).

Publication types

  • Research Support, N.I.H., Extramural
  • Validation Study

MeSH terms

  • Chromatography, Liquid / methods*
  • Digitoxin / blood
  • Digitoxin / chemistry
  • Digitoxin / urine
  • Digoxin / blood*
  • Digoxin / chemistry
  • Digoxin / urine*
  • Female
  • Humans
  • Mass Spectrometry / methods*
  • Pregnancy
  • Reproducibility of Results
  • Sensitivity and Specificity


  • Digoxin
  • Digitoxin