Interference of hawthorn on serum digoxin measurements by immunoassays and pharmacodynamic interaction with digoxin.
BACKGROUND
Hawthorn is an herb indicated for treating cardiac illness. Because a patient taking digoxin may also take hawthorn, we investigated potential interference of hawthorn in serum digoxin measurements using immunoassays as well as pharmacodynamic interaction between hawthorn and digoxin. Hawthorn contains alkaloids that are structurally similar to digoxin and may interfere with serum digoxin measurement using immunoassays. In addition, hawthorn has cardioactive properties similar to digoxin.


OBJECTIVE
To study potential pharmacodynamic interaction between hawthorn and digoxin.


METHODS
The effects of hawthorn extract on serum digoxin measurements using Digoxin III (Abbott Laboratories, Abbott Park, Illinois) and the Tina-Quant digoxin assay (Roche Diagnostics, Indianapolis, Indiana) were investigated using 2 different brands of extract. To study the pharmacodynamic interaction between hawthorn and digoxin, we used an isolated adult rat cardiomyocyte system, measuring calcium transients by real-time fluorescence spectrophotometry.


RESULTS
Hawthorn interfered only with the Digoxin III immunoassay but had no effect on the Tina-Quant assay. Both hawthorn extracts increased intracellular calcium levels, but the lack of additive response with digoxin suggests both may bind to the same site of Na, K adenosine triphosphatase.


CONCLUSIONS
Because of interference of hawthorn with a digoxin immunoassay and pharmacodynamic interaction with digoxin, a patient receiving digoxin should avoid hawthorn.
Dasgupta
Amitava
A
Department of Pathology and Laboratory Medicine, University of Texas-Houston Medical School, Houston, TX 77030, USA. Amitava.Dasgupta@uth.tmc.edu
Kidd
Laura
L
Poindexter
Brian J
BJ
Bick
Roger J
RJ
D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured; D000075202:Contraindications; D027825:Crataegus / Q000737:chemistry*; D004077:Digoxin / Q000097:blood* / Q000494:pharmacology*; D004347:Drug Interactions; D007118:Immunoassay; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D014966:Xanthenes
D000814:Aniline Compounds; C409648:Fluo 4; D010936:Plant Extracts; D014966:Xanthenes; D004077:Digoxin; D002118:Calcium