Therapeutic drug monitoring of digoxin: impact of endogenous and exogenous digoxin-like immunoreactive substances.
Digoxin is a cardioactive drug with a narrow therapeutic range. Therapeutic drug monitoring is essential in clinical practice for efficacy as well as to avoid digoxin toxicity. Immunoassays are commonly used in clinical laboratories for determination of serum or plasma digoxin concentrations. Unfortunately, digoxin immunoassays are affected by both endogenous and exogenous compounds. Endogenous compounds are termed 'digoxin-like immunoreactive substances' (DLIS), which are found in elevated concentrations in volume-expanded patients. Exogenous compounds that interfere with digoxin assays are various drugs such as spironolactone, potassium canrenoate as well as Digibind (Fab fragment of antidigoxin antibody), which is used in treating life-threatening digoxin overdose. Moreover, various Chinese medicines such as Chan Su, Lu-Shen Wan and oleander-containing herbal preparations also interfere with serum digoxin measurements by immunoassays. Monitoring unbound (free) digoxin concentration may under certain circumstances eliminate such interferences. Clinicians should be aware of limitations of therapeutic drug monitoring of digoxin using immunoassays.
Dasgupta
Amitava
A
Department of Pathology and Laboratory Medicine, University of Texas-Houston Medical School, Houston, Texas 77030, USA. Amitava.Dasgupta@uth.tmc.edu
D002298:Cardenolides / Q000097:blood* / Q000737:chemistry / Q000276:immunology; D003429:Cross Reactions; D004077:Digoxin / Q000097:blood* / Q000276:immunology / Q000627:therapeutic use*; D004347:Drug Interactions; D016903:Drug Monitoring; D004365:Drugs, Chinese Herbal; D006801:Humans; D012503:Saponins / Q000097:blood* / Q000737:chemistry / Q000276:immunology
D002298:Cardenolides; D004365:Drugs, Chinese Herbal; D012503:Saponins; C034504:digoxin-like factors; D004077:Digoxin