Animal Study Shows Ephedrine Increases Arrhythmia Risk

OKLAHOMA CITY--Ephedrine appears to increase ischemia-dependent heart attack when consumed at levels recommended by dietary supplements, according to researchers from the University of Oklahoma Health Sciences Center. In a study published in the Journal of the American College of Cardiology (44, 8:1675-78, 2004) (www.cardiosource.com), researchers gave ephedrine (as Xenadrine, 0.4 mg/kg/d) to 15 dogs at low risk for ventricular fibrillation (VF) during exercise and transient myocardial ischemia 30 days after a small anterior heart attack. After five days, nine dogs had increased arrhythmia and four had VF, which killed three of the animals.

Philip B. Adamson, M.D., lead researcher, addressed the results during the American Medical Association's 23rd Annual Science Reporters Conference on Oct. 14. "We wanted to determine how ephedrine, taken as directed, might cause someone with ischemic heart disease to have a potentially fatal heart attack," he said. "Ephedrine looks benign when you look at its effects on normal heart rates, but when there is a blockage, boom, ephedrine starts a potentially lethal arrhythmia."

According to Adamson, ephedrine worked to hyperstimulate the sympathetic nervous system, increasing the risk of instability in the electro-physiology of the heart. He noted the study supports the decision of the Food and Drug Administration (FDA) to ban ephedra-containing dietary supplements.