Homogeneous Immunoassays—Therapeutic Drug Monitoring
Innofluor®—Fluorescence Polarization Immunoassays To view and print the files below you will need Adobe Acrobat Reader®,
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INNOFLUOR® Digoxin Assay System
The INNOFLUOR® DIGOXIN Assay System is intended for the quantitative determination of total digoxin in serum for therapeutic drug monitoring by fluorescence polarization immunoassay (FPIA). The assay system is for use on the TDx® or the TDxFlxTM (TDx®/TDxFLx®) analyzer.
Digoxin is a cardiac glycoside prescribed for the treatment of congestive heart failure and cardiac arrhythmias.1-3 Cardiac glycosides appear to inhibit membrane-bound Na,K-ATPase which leads to increased calcium availability and results in improved cardiac muscle contractions.3,4
Digoxin undergoes a 6-8 hour distribution phase following routine oral or intravenous administration. At steady state, digoxin is distributed to most body tissues and is about 20-25% bound to protein in plasma.2,3 the majority of digoxin is eliminated unchanged in the urine, with an average half-life of 1.6 days.2 As renal function decreases or is impaired by co-administered drugs renal elimination of digoxin decreases and the small amount of digoxin metabolized in the liver increases.5 Metabolites of digoxin include digoxigenin, the mono- and bis- digitoxosides, and dihydrodigoxin.6,7
Cardiac glycosides have a narrow therapeutic range and are frequently toxic, with many of the toxicity symptoms similar to symptoms of the underlying disearse.2-4,8 It is important to monitor serum levels in combination with the information provided by clinical data to avoid toxicity while maintaining adequate dosing.6-8 HPLC and RIA have been used to quantitate serum digoxin levels.2,4,8,9
Wettrell G, Anderson KE. Cardiovascular drugs II: digoxin. Ther Drug Monitoring 1986; 8: 129-139.
Barnhart ER. Pub. Physician’s Desk Reference. Oradell, NJ: Medical Economics Co., Inc., 1991: 760-775.
Hoffman BF, Bigger JT Jr. Digitalis and allied cardiac glycosides. In: The pharmacological basis of therapeutics, Goodman Gilman A, et. al., eds. Pergamon Tress Inc., New York 10523 1990; 814-839.
Meyers FH. Jawetz E, Goldfin A. Digitalis. In: Review of medical pharmacology, 7th ed. Los Altos CA: Lange Medical Publications, 1980: 135-146.
Lewis RP. Clinical use of serum digoxin concentrations. Am J Cardiol 1992; 69(18): G97-107.
Baselt RC. Digitoxin. In: Disposition of toxic drugs and chemicals in man, 2nd ed. Davis, CA: Biomedical Publications, 1982: 254-257.
Kelly RA, Smith TW. Recognition and management of digitalis toxicity. Am J Cardiol 1992; 69: G108-109.
Bussey HI, Hawkins, DW, et al. A comparative trial of digoxin and digitoxin in the treatment of congestive heart failure. Pharmacoltherapy 188; 8(4): 235-240.
