Related Experiment Video
Updated: Jun 10, 2026

Diagonal Method to Measure Synergy Among Any Number of Drugs
Published on: June 21, 2018
Interference of hawthorn on serum digoxin measurements by immunoassays and pharmacodynamic interaction with digoxin
Amitava Dasgupta1, Laura Kidd, Brian J Poindexter
1Department of Pathology and Laboratory Medicine, University of Texas-Houston Medical School, Houston, TX 77030, USA. Amitava.Dasgupta@uth.tmc.edu
Context:
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.
Design:
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.
Conclusion:
Because of interference of hawthorn with a digoxin immunoassay and pharmacodynamic interaction with digoxin, a patient receiving digoxin should avoid hawthorn.
Related Concept Videos
Drug toxicity: Drug–Drug Interaction
Pharmacokinetics: Drug–Drug Interactions
Heart Failure Drugs: Inotropic Agents
Pharmacokinetics: Drug–Food and Drug–Viral Interactions
Therapeutic Drug Monitoring: Drug Analysis Methods
Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers
Verapamil, a calcium channel blocker, inhibits calcium movement across myocardial cell membranes and vascular smooth muscle. This results in the dilation of coronary and...
