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Homogeneous Immunoassays—Therapeutic Drug Monitoring
QMS®—Latex Enhanced Immunoturbidimetric Assays
Digitoxin Assay System
The DIGITOXIN Assay System is intended for the quantitative determination of total digitoxin in serum for therapeutic drug monitoring.
Digitoxin is a cardiac glycoside prescribed for the treatment of congestive heart failure and cardiac arrhythmias.1,2 Cardiac glycosides appear to inhibit membrane-bound Na,K-ATPase which leads to increased calcium availability and results in improved cardiac muscle contractions.2,3
Digitoxin is routinely administered orally. At steady state, digitoxin is distributed in most body tissues and is over 90% protein bound in plasma.1,2 Digitoxin is metabolized in the liver, excreted with the bile into the intestine and recirculated through the liver until completely metabolized.1 Metabolism is complex and results in the formation of many metabolites, which are primarily inactive and are probably excreted in the urine.4,5 Digoxin is also a metabolite but comprises only a small fraction of the total metabolites during chronic therapy.1,4 The long elimination half-life of 6-8 days is most likely due to the firm binding of digitoxin to protein and is not significantly affected by liver disease.1,2,6
Cardiac glycosides have a narrow therapeutic range and are frequently toxic, with many of the toxicity symptoms similar to symptoms of the underlying disease.1-3,7 It is important to monitor serum levels in combination with information provided by clinical data to avoid toxicity while maintaining adequate dosin.4,5
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